Stylus and sensor controller

ABSTRACT

A stylus is provided, which includes a core body, an electrode disposed adjacent to the core body, a transmitter that sends a downlink signal including switch information SW 1  using the electrode, and a controller that determines whether the stylus is in contact state in which the core body is held in contact with an operating surface or the stylus is in hover state in which the core body is not held in contact with the operating surface. In the contact state, the controller controls the transmitter to send the switch information SW 1  at a first bit rate (e.g., data (E)). In the hover state, the controller controls the transmitter to send the switch information SW 1  at a second bit rate smaller than the first bit rate (e.g., data (C)). A technical advantage includes lowering the possibility of a failure to receive downlink signals when the stylus is in hover state, even though the stylus sends the downlink signals with the same intensity as when the stylus is in contact state.

BACKGROUND Technical Field

The present disclosure relates to a stylus and a sensor controller, andmore particularly to a stylus that sends downlink signals whilehovering, and a sensor controller that receives such downlink signals.

Description of the Related Art

There is a stylus capable of sending, to a sensor controller, a positiondetecting signal (position signal) and a signal including various datasuch as a unique IDentification (ID), a pen pressure, etc. (datasignal). Signals that a stylus sends to a sensor controller willhereinafter be collectively referred to as “downlink signals.” PatentDocuments 1 through 3 disclose examples of styluses that send downlinksignals.

When a user of a stylus tries to input characters and pictures using thestylus, the stylus gradually approaches the touch surface of anelectronic device including a sensor controller until finally the corebody of the stylus contacts the touch surface. Characters and picturescan be entered through the stylus while the core body of the stylus isheld in contact with the touch surface. The state in which the core bodyof the stylus is held in contact with the touch surface will hereinafterbe referred to as “contact” state, whereas the state in which the corebody of the stylus is not yet in contact with the touch surface as“hover” state.

Patent Document 2 discloses a stylus that suppresses the intensity of aposition signal sent from the stylus in contact state to a smaller valuethan the intensity of a position signal sent from the stylus in hoverstate (Patent Document 2, paragraph 4, line 57 through paragraph 5, line3).

Patent Document 3 discloses a stylus that sends a position signal andonly some additional signals intermittently in predetermined periodiccycles in hover state and sends a signal representing a pen pressure inthe intervals (gaps) in contact state (Patent Document 3, paragraph 13,line 33 through paragraph 14, line 46, FIGS. 9A through 9C).

PRIOR ART DOCUMENT Patent Documents

Patent Document 1: PCT Patent Publication No. WO2015/111159

Patent Document 2: U.S. Patent No. 8773405

Patent Document 3: U.S. Patent No. 8536471

BRIEF SUMMARY Technical Problems

Comparison of the signal/noise (S/N) ratios of downlink signals receivedby a sensor in the touch surface between when the stylus is in hoverstate and when the stylus is in contact state indicates that the S/Nratio is smaller when the stylus is in hover state. This is because whenthe stylus is in hover state, the stylus is spaced from the sensor by alarger distance, and the downlink signal is attenuated to a greaterextent. According to the conventional art, as a result, the sensorcontroller may fail to receive the downlink signal while the stylus isin hover state. It has been desirous of address this technicalchallenge.

The technology disclosed in Patent Document 2 may be considered to beable to lower the possibility of a failure to receive the downlinksignal while the stylus is in hover state because the intensity of adownlink signal while the stylus is in hover state is made stronger thanthe intensity of a downlink signal while the stylus is in contact state.However, the technology suffers from another problem in that the stylusrequires a special transmitter capable of sending signals with avariable intensity.

Therefore, it is an aspect of the present disclosure to provide a stylusand a sensor controller which are capable of lowering the possibility ofa failure to receive downlink signals when the stylus is in hover stateeven though the stylus sends the downlink signals with the sameintensity as when the stylus is in contact state.

Technical Solution

A stylus according to an aspect of the present disclosure includes acore body, an electrode disposed adjacent to the core body, atransmitter that sends a signal including a first digital value usingthe electrode, and a controller that controls the transmitter. Thecontroller determines whether the stylus is in contact state in whichthe core body is held in contact with an operating surface or the stylusis in hover state in which the core body is not held in contact with theoperating surface, controls the transmitter to send the first digitalvalue at a first bit rate if the result of the determination indicatesthe contact state, and controls the transmitter to send the firstdigital value at a second bit rate smaller than the first bit rate ifthe result of the determination indicates the hover state.

A stylus according to another aspect of the present disclosure includesa core body, an electrode disposed adjacent to the core body, atransmitter that sends a signal including a first digital value usingthe electrode, and a controller that controls the transmitter. Thecontroller controls the transmitter to send the signal in units of asuperframe including a predetermined number of frames. The controllercontrols the transmitter to send, in each of the predetermined number offrames, a frame index number representing order of the frames in thesuperframe.

A stylus according to still another aspect of the present disclosureincludes a core body, an electrode disposed adjacent to the core body, atransmitter that sends a signal including a first digital value usingthe electrode, and a controller that determines whether the stylus is incontact state in which the core body is held in contact with anoperating surface or the stylus is in hover state in which the core bodyis not held in contact with the operating surface. The controllercontrols the transmitter to send the first digital value according to afirst signal transmission process if the result of the determinationindicates the contact state, and controls the transmitter to send thefirst digital value according to a second signal transmission processwhose decoding error rate is smaller than the first signal transmissionprocess if the result of the determination indicates the hover state.

A sensor controller according to the present disclosure acquires stateinformation of a stylus from a signal received from the stylus accordingto a first demodulation process. If the state information indicates thatthe stylus is in hover state, the sensor controller acquires a firstdigital value to be included subsequently to the state informationaccording to the first demodulation process. If the state informationindicates that the stylus is in contact state, the sensor controlleracquires the first digital value to be included subsequently to thestate information according to a second demodulation process whose biterror rate is higher than the first demodulation process.

Advantageous Effects

According to the present disclosure, since the noise resistance in hoverstate is improved, there are obtained advantages including a reductionin the non-detection ratio of downlink signals, a reduction in the biterror detection ratio at the time downlink signals are modulated ordecoded, and a reduction in the decoding error ratio while taking errorcorrection into consideration. Thus, even if downlink signals are sentwith the same transmission intensity as in contact state, thepossibility of a failure to receive downlink signals in hover state canbe lowered.

According to the present disclosure, furthermore, since each frame has aframe index number, when the stylus sends one piece of information asdivided over a plurality of frames, the sensor controller on a receptionside can correctly recover the information on the basis of the frameindex numbers even when the divided information is received out oforder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram depicting an arrangement of an electronic device 3according to an embodiment of the present disclosure. FIG. 1(a) depictsa mode of operation of the electronic device 3 for detecting a touch bya finger F, and FIG. 1(b) depicts a mode of operation of the electronicdevice 3 for detecting a stylus 2.

FIG. 2 is a diagram depicting an arrangement of the electronic device 3according to the embodiment of the present disclosure.

FIG. 3 is a diagram depicting configurations of a long burst signal, aburst signal, and a data signal that are sent by the stylus 2 accordingto the embodiment of the present disclosure.

FIG. 4 is a diagram depicting sequences of signals sent and receivedbetween the stylus 2 and a sensor controller 31 when the stylus 2 isabove an uplink detection height AH. FIG. 4(a) depicts the sequence inwhich the sensor controller 31 sends a pen trigger signal, and FIG. 4(b)depicts the sequence in which the sensor controller 31 requests that along burst signal be sent.

FIG. 5 is a diagram depicting sequences of signals sent and receivedbetween the stylus 2 and the sensor controller 31 when the stylus 2 iswithin a sensing range SR and the sensor controller 31 has not yetidentified the position of the stylus 2. FIG. 5(a) depicts the sequencein which the sensor controller 31 sends a pen trigger signal, FIG. 5(b)depicts the sequence in which the sensor controller 31 receives a longburst signal sent by the stylus 2, using linear electrodes 30Y, and FIG.5(c) depicts the sequence in which the sensor controller 31 receives along burst signal sent by the stylus 2, using linear electrodes 30X.

FIG. 6 is a diagram depicting a sequence of signals sent and receivedbetween the stylus 2 and the sensor controller 31 when the stylus 2 iswithin the sensing range SR and after the sensor controller 31 hasidentified the position of the stylus 2. FIG. 6 depicts the sequence inwhich the stylus 2 sends a burst signal and a data signal (data to besent is not a unique ID) in hover state.

FIG. 7 is a diagram illustrative of the manner in which the sensorcontroller 31 operates according to the embodiment of the presentdisclosure. FIG. 7(a) depicts a first half of a full-range scanningprocess, FIG. 7(b) depicts a latter half of the full-range scanningprocess, and FIG. 7(c) depicts a sector scanning process.

FIG. 8 is a diagram depicting an arrangement of the stylus 2 accordingto the embodiment of the present disclosure.

FIG. 9 is a flowchart of an overall processing sequence performed by thesensor controller 31 while the stylus 2 is hovering, according to theembodiment of the present disclosure.

FIG. 10 is a diagram depicting a format of downlink signals that is sentby the stylus 2 according to the embodiment of the present disclosure.

FIG. 11 is a flowchart of a process of receiving uplink signals and aprocess of sending downlink signals, which are carried out by the stylus2 according to the embodiment of the present disclosure.

FIG. 12 is a flowchart of a process of sending uplink signals and aprocess of receiving downlink signals, which are carried out by thesensor controller 31 according to the embodiment of the presentdisclosure.

FIG. 13 is a flowchart of the process of sending uplink signals and theprocess of receiving downlink signals, which are carried out by thesensor controller 31 according to the embodiment of the presentdisclosure.

FIG. 14 is a diagram depicting a first example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2 according to the embodiment of the present disclosure.

FIG. 15 is a diagram depicting a second example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2 according to the embodiment of the present disclosure.

FIG. 16 is a diagram depicting a third example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2 according to the embodiment of the present disclosure.

FIG. 17 is a diagram depicting a fourth example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2 according to the embodiment of the present disclosure.

FIG. 18 is a diagram depicting a fifth example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2 according to the embodiment of the present disclosure.

FIG. 19 is a diagram depicting a sixth example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2 according to the embodiment of the present disclosure.

FIG. 20 is a diagram depicting an arrangement of a stylus 2 according toa first modification of the embodiment of the present disclosure.

FIG. 21 is a flowchart of a process of receiving uplink signals and aprocess of sending downlink signals, which are carried out by a stylus 2according to a second modification of the embodiment of the presentdisclosure.

DETAILED DESCRIPTION

An embodiment of the present disclosure will be described in detailbelow with reference to the accompanying drawings. First, an outline ofarrangements and operation of a stylus 2 and a sensor controller 31according to the present embodiment will be described below withreference to FIGS. 1 through 8, and then operation of the stylus 2 andthe sensor controller 31 related to the features of the presentdisclosure will be described below with reference to FIGS. 9 through 19.

FIG. 1 is a diagram depicting an arrangement of an electronic device 3according to the present embodiment. The electronic device 3 is acomputer having a touch surface (operating surface) such as a tabletterminal, for example, and includes a sensor 30 and a sensor controller31, as depicted in FIG. 1.

The sensor 30 includes a matrix of electrodes including M linearelectrodes 30X (first electrodes) and N (N<M) linear electrodes 30Y(second electrodes) that are disposed inside the touch surface.According to a specific example, M=72, N=46. The M linear electrodes 30Xextend at equal intervals in a first direction parallel to the touchsurface. The N linear electrodes 30Y extend at equal intervals in asecond direction parallel to the touch surface and perpendicular to thefirst direction. The linear electrodes 30X and the linear electrodes 30Yare respectively connected to the sensor controller 31.

The sensor 30 is disposed in combination with a display panel (notdepicted) such as a liquid crystal display panel or the like. The sensor30 may be combined with the sensor 30 in desired specific layouts. Forexample, those layouts include the out-cell type in which the linearelectrodes 30X and 30Y are disposed outside the display panel, theon-cell type in which the linear electrodes 30X and 30Y are disposed ona color filter glass panel or substrate glass panel within the displaypanel, and the in-cell type in which drive electrodes (specifically,common electrodes or pixel electrodes) of the display panel double asthe linear electrodes 30X or 30Y.

The sensor controller 31 is a controller that detects, via the sensor30, a touch by a finger F (also deriving positional coordinates offinger F on the touch surface) and detecting, via the sensor 30, thestylus 2 (also deriving positional coordinates of the stylus 2 on thetouch surface), in a time-division fashion.

FIG. 1(a) depicts a mode of operation of the electronic device 3 fordetecting a touch by finger F. As depicted in FIG. 1(a), for detecting atouch by finger F, the sensor controller 31 supplies the linearelectrodes 30Y successively with a predetermined signal (hereinafterreferred to as “finger detecting signal”) and successively scanspotentials of the linear electrodes 30X to detect the finger detectingsignal that has reached the linear electrodes 30X via the intersectionsbetween the linear electrodes 30Y and 30X. The amplitude of the fingerdetecting signal that is detected in this manner is smaller when fingerF is close to the intersection via which the finger detecting signal haspassed, than when finger F is not close to the intersection. This isbecause part of the electric current that flows through the linearelectrodes 30X and 30Y flows toward the human body via capacitivecoupling between finger F and the linear electrodes 30X and 30Y. Thesensor controller 31 detects a touch by finger F by detecting thischange in the amplitude.

FIG. 1(b) depicts a basic mode of operation of the electronic device 3for detecting the stylus 2. As depicted in FIG. 1(b), in the basic modeof operation for detecting the stylus 2, the sensor controller 31performs a detecting operation on a signal (hereinafter referred to as“downlink signal”) sent by the stylus 2, using the linear electrodes 30Xand 30Y successively as reception electrodes. The sensor controller 31detects the stylus 2 based on the detected downlink signal. In actualoperation, there is a situation in which the sensor controller 31detects the stylus 2 using only some of the linear electrodes 30X and30Y. Such a situation will be described later.

In order for the sensor controller 31 to detect the stylus 2, it isnecessary for the stylus 2 to be so close to the touch surface of theelectronic device 3 that the sensor controller 31 can receive thedownlink signal. A sensing range SR that is illustrated in FIG. 1(b) isa schematic representation of a range in which the sensor controller 31can receive the downlink signal. When the stylus 2 enters the sensingrange SR, the sensor controller 31 detects the downlink signal, therebydetecting the stylus 2. The movement of the stylus 2 from outside thesensing range SR into the sensing range SR will hereinafter be referredto as “pen-down.” The pen-down is usually performed by an action of theuser to bring the stylus 2 closer to the touch surface of the electronicdevice 3. The hover state described above is a state in which the stylus2 has entered the sensing range SR by way of pen-down, but has not yetbeen in contact with the touch surface.

Even when the stylus 2 is outside the sensing range SR, there areinstances in which the stylus 2 is able to receive signals (hereinafterreferred to as “uplink signals”) that the sensor controller 31 has sentto the stylus 2. This is because some uplink signals (a pen triggersignal, a command signal that instructs the stylus 2 to send a longburst signal, etc. to be described later) are sent using the touchsurface in its entirety (all of the linear electrodes 30X or all of thelinear electrodes 30Y or both of them). An uplink detection height AHthat is also illustrated indicates a limitation on the height (distancefrom the touch surface) up to which the stylus 2 can receive thoseuplink signals. The uplink detection height AH is at a position higher(a position farther from the touch surface) than the upper limit of thesensing range SR.

FIG. 2 is a diagram depicting an arrangement of the electronic device 3according to the present embodiment. The linear electrodes 30X and thelinear electrodes 30Y of the sensor 30 form capacitive coupling with thestylus 2 and with finger F. When finger F approaches the sensor 30, partof an electric current flowing from the sensor controller 31 to thelinear electrodes 30Y is drawn into finger F through the capacitivecoupling. Since the amplitude of the finger detecting signal detected bythe linear electrodes 30X is now reduced, as described above, the sensorcontroller 31 is able to detect a touch by finger F. The sensor 30 isarranged to be able to send and receive signals bidirectionally to andfrom the stylus 2 through the capacitive coupling.

As depicted in FIG. 2, the sensor controller 31 includes a transmitter60, a selector 40, a receiver 50, a logic unit 70, and a microcontroller unit (MCU) 80.

The transmitter 60 is a circuit that generates a finger detecting signalat the timing to detect a touch by finger F, and generates uplinksignals at the timing to detect the stylus 2. The uplink signals includea pen trigger signal that lets the stylus 2 know the existence of thesensor controller 31 and a command signal representing a command for thestylus 2.

FIG. 2 illustrates in detail the transmitter 60 including functionalblocks involved in the generation of uplink signals. The functionalblocks include a pattern supply 61, a switch 62, a spreading processor63, a code train holder 64, and a transmission guard 65. In the presentembodiment, the pattern supply 61 will be described as included in thetransmitter 60. However, the pattern supply 61 may be included in theMCU 80.

The pen trigger signal includes a repetition of a predetermineddetection pattern c1 and a predetermined delimiter pattern STP at theend.

The detection pattern cl is a pattern of symbol values used for thestylus 2 to detect the existence of the sensor controller 31, and isknown to the stylus 2 in advance (before the stylus 2 detects the sensorcontroller 31). A symbol is a unit of information used for modulation ina transmission process (a unit of information represented by atransmission signal), and is a unit of information obtained bydemodulating one symbol, as a reception signal, in a reception process.The symbol values may include a value that is converted into a bit trainby the stylus 2 having received a symbol (hereinafter referred to as“bit train correlated value”) and a value that is not converted into abit train by the stylus 2 (hereinafter referred to as “bit trainuncorrelated value”). According to a specific example, the detectionpattern c1 includes a pattern “PM” made up of two (2) bit trainuncorrelated values “P” and “M.”

The delimiter pattern STP is a pattern of symbol values for notifyingthe stylus 2 of the end of the repetition period of the detectionpattern c1, and includes a pattern that does not appear in therepetition of the detection pattern c1. The delimiter pattern STP isalso known to the stylus 2 in advance (before the stylus 2 detects thesensor controller 31). According to an example, if the detection patterncl includes a pattern “PM” made up of two bit train uncorrelated values“P” and “M,” as described above, then the delimiter pattern STP mayinclude a pattern “PP” made up of two consecutive bit train uncorrelatedvalues “P.” The delimiter pattern STP and the detection pattern c1 maybe switched around such that the delimiter pattern STP includes apattern “PM” and the detection pattern c1 includes a pattern “PP.”

The pattern supply 61 holds the detection pattern c1 and the delimiterpattern STP, and outputs these patterns in a predetermined order inaccordance with the instruction of a control signal ctrl_t1 suppliedfrom the logic unit 70. Specifically, the pattern supply 61 repeatedlyoutputs the detection pattern c1 in succession (continuously) during apredetermined successive transmission period, and outputs the delimiterpattern STP immediately after the successive transmission period isfinished. In this manner, the pen trigger signal is sent. The delimiterpattern STP may be output at the beginning of a command signalindicating an instruction to send a long burst signal, to be describedlater.

The switch 62 has a function to select either the pattern supply 61 orthe MCU 80 based on a control signal ctrl_t2 supplied from the logicunit 70, and to supply an output signal from the selected one to thespreading processor 63. If the switch 62 selects the pattern supply 61,then the spreading processor 63 is supplied with the detection patternc1 or the delimiter pattern STP from the pattern supply 61. If theswitch 62 selects the MCU 80, then the spreading processor 63 issupplied with control information c2 from the MCU 80.

The control information c2 includes information representing aninstruction (command) for the stylus 2, and is generated by the MCU 80.The command signal described above includes the control information c2.The control information c2 is different from the detection pattern c1and the delimiter pattern STP in that it includes symbol values (forexample, 0 through 15) correlated to a variable-length bit train andthese symbol values are not shared with the stylus 2 in advance.

The code train holder 64 has a function to generate and hold a spreadcode PN of a predetermined chip length having autocorrelationcharacteristics, on the basis of a control signal ctrl_t3 supplied fromthe logic unit 70. The spread code PN held by the code train holder 64is supplied to the spreading processor 63.

The spreading processor 63 has a function to obtain a transmission chiptrain having a predetermined chip length by modulating the spread codePN held by the code train holder 64 on the basis of the symbol values(the detection pattern c1, the delimiter pattern STP, or the controlinformation c2) supplied via the switch 62. The spreading processor 63supplies the acquired transmission chip train to the transmission guard65.

The transmission guard 65 has a function to insert a guard period (aperiod in which neither transmission nor reception is carried out) thatis required to switch between a transmission operation and a receptionoperation, between a transmission period for uplink signals and areception period for downlink signals, on the basis of a control signalctrl_t4 supplied from the logic unit 70.

The receiver 50 is a circuit that receives a finger detecting signalsent by the transmitter 60 or downlink signals sent by the stylus 2 onthe basis of a control signal ctrl_r from the logic unit 70.Specifically, the receiver 50 includes an amplifying circuit 51, adetecting circuit 52, and an analog-to-digital (AD) converter 53.

The amplifying circuit 51 amplifies and outputs a signal (a fingerdetecting signal or downlink signals) supplied from the selector 40. Thedetecting circuit 52 is a circuit that generates a voltage commensuratewith the level of an output signal from the amplifying circuit 51. TheAD converter 53 is a circuit that generates a digital signal by samplingthe voltage output from the detecting circuit 52 at predetermined timeintervals. The digital signal output by the AD converter 53 is suppliedto the MCU 80.

A signal receiving process performed by the detecting circuit 52includes a process of detecting a signal during a period that depends ona length of the period of a signal sent by the stylus 2 (a first bitrate and a second bit rate to be described later), depending on thewhether the stylus is in hover state or in contact state. The MCU 80acquires data sent by the stylus 2 (switch information SW1, etc. to bedescribed later) by determining the bit value of a signal according to ademodulation process that corresponds to a modulation process usedaccording to whether the stylus is in hover state or in contact state.If an error detecting code is included in a frame sent by the stylus 2,then the MCU 80 detects errors (or corrects errors) based on the errordetecting code in demodulating data sent by the stylus 2 (switchinformation SW1, etc. to be described later).

The selector 40 includes switches 44 x and 44 y and conductor selectingcircuits 41 x and 41 y.

The switches 44 x and 44 y include one-circuit two-contact switchelements, where a common terminal is selectively connected to either oneof T terminal and R terminal. The common terminal of the switch 44 x isconnected to the conductor selecting circuit 41 x, T terminal of theswitch 44 x is connected to the output terminal of the transmitter 60,and R terminal of the switch 44 x is connected to the input terminal ofthe receiver 50. The common terminal of the switch 44 y is connected tothe conductor selecting circuit 41 y, T terminal thereof is connected tothe output terminal of the transmitter 60, and R terminal thereof isconnected to the input terminal of the receiver 50.

The conductor selecting circuit 41 x is a switch element for selectivelyconnecting the M linear electrodes 30X to the common terminal of theswitch 44 x. The conductor selecting circuit 41 x is capable ofconnecting some or all of the M linear electrodes 30X simultaneously tothe common terminal of the switch 44 x.

The conductor selecting circuit 41 y is a switch element for connectingthe N linear electrodes 30Y selectively to the common terminal of theswitch 44 y. The conductor selecting circuit 41 y is arranged to be ableto connect some or all of the N linear electrodes 30Y simultaneously tothe common terminal of the switch 44 y.

The selector 40 is supplied with four control signals sTRx, sTRy, selX,and selY from the logic unit 70. Specifically, the control signal sTRxis supplied to the switch 44 x, the control signal sTRy to the switch 44y, the control signal selX to the conductor selecting circuit 41 x, andthe control signal selY to the conductor selecting circuit 41 y. Thelogic unit 70 controls the selector 40 using these control signals sTRx,sTRy, selX, and selY to send and receive a finger detecting signal, senduplink signals including a pen trigger signal and a command signal, andreceive downlink signals. The controlling of the selector 40 by thelogic unit 70 will be described in greater detail later.

The logic unit 70 and the MCU 80 serve as a controller that controls thetransmitter 60, the receiver 50, and the selector 40, to thereby controltransmitting and receiving operation of the sensor controller 31.Specifically, the MCU 80 includes a microprocessor that has a read-onlymemory (ROM) and a random-access memory (RAM) therein and operatesaccording to predetermined programs. The logic unit 70 is arranged tooutput control signals described above under the control of the MCU 80.The MCU 80 is arranged to perform a process of deriving coordinate datax and y indicating the position of finger F or the stylus 2 on the basisof a digital signal supplied from the AD converter 53 and outputting thederived coordinate data x and y to a system controller of the electronicdevice 3. The MCU 80, if the digital signal supplied from the ADconverter 53 indicates a data signal, performs a process of acquiringdata Res represented by the digital signal and outputting the acquireddata Res to the system controller of the electronic device 3.

The controlling of the selector 40 by the logic unit 70 will bedescribed in specific detail below.

For sending and receiving a finger detecting signal, the logic unit 70controls the selector 40 using the control signals sTRx, sTRy, selX, andselY, so that N linear electrodes 30Y are successively connected to theoutput terminal of the transmitter 60 and the M linear electrodes 30Xare successively connected to the input terminal of the receiver 50. Asdepicted in FIG. 1, it is possible to supply a finger detecting signalsuccessively to the N linear electrodes 30Y and detect, with thereceiver 50, the finger detecting signal that has reached the linearelectrodes 30X through the intersections of the linear electrodes 30Yand 30X, thereby detecting a touch by finger F.

For sending uplink signals and receiving downlink signals, the logicunit 70 performs different processes depending on the manner in whichthe stylus 2 is detected and the types of downlink signals. The types ofdownlink signals and sequences of signals sent and received between thestylus 2 and the sensor controller 31 will first be described below, andthen the manner in which the logic unit 70 operates to send uplinksignals and receive downlink signals will be described in detail.

FIG. 3 is a diagram depicting the types of downlink signals sent by thestylus 2 according to the embodiment of the present disclosure. Asdepicted in FIG. 3, the downlink signals include a long burst signal, aburst signal, and a data signal. The long burst signal includes a signalhaving a predetermined waveform as a predetermined pattern known inadvance between the stylus 2 and the sensor controller 31. The longburst signal is sent continuously over a predetermined time period T1.The burst signal includes the above signal having the predeterminedwaveform, but is sent continuously over a predetermined time period T4shorter than the time period T1. The data signal includes a data signalgenerated by modulating the above signal having the predeterminedwaveform with data. Typically, the data signal is sent subsequently tothe burst signal over a time period corresponding to the difference,T1-T4, between the time period T4 and the time period T1. Actually,however, there is an instance in which the transmission of the datasignal continues over a time longer than the difference T1-T4, asdescribed later. A predetermined gap signal (not depicted) fordelimiting the burst signal is inserted at the beginning of the burstsignal. The types of the downlink signals to be sent by the stylus 2 areselected according to the instruction of command signals sent by thesensor controller 31.

FIGS. 4 through 6 are diagrams depicting sequences of signals sent andreceived between the stylus 2 and the sensor controller 31. FIG. 4depicts the sequences when the stylus 2 is above the uplink detectionheight AH, FIG. 5 depicts the sequences when the stylus 2 is within thesensing range SR and the sensor controller 31 has not yet identified theposition of the stylus 2, and FIG. 6 depicts the sequence when thestylus 2 is within the sensing range SR and the sensor controller 31 hasidentified the position of the stylus 2. These sequences will berespectively described below.

When the Stylus 2 is Above the Uplink Detection Height AH

FIG. 4(a) depicts the sequence in which the sensor controller 31 sends apen trigger signal and FIG. 4(b) depicts the sequence in which thesensor controller 31 requests that a long burst signal be sent.

As depicted in FIG. 4(a), the sensor controller 31 sends a pen triggersignal over a time period Ts (=t1−t0) from time t0 to time t1. Thesensor controller 31 sends the pen trigger signal when it has not yetdetected the stylus 2. As described above, the pen trigger signalincludes a repetition of a predetermined detection pattern c1 and apredetermined delimiter pattern STP at the end. The stylus 2intermittently performs a detecting operation to detect the detectionpattern c1 by intermittently performing a detecting operation to detectthe symbols (“P” and “M” in the above example) of the detection patternc1. If the stylus 2 is above the uplink detection height AH, then itcannot detect the detection pattern c1 with its detecting operation.Therefore, the stylus 2 simply repeats the detecting operation to detectthe detection pattern c1.

As depicted in FIG. 4(b), subsequently to the transmission of the pentrigger signal, the sensor controller 31 starts sending a command signal(denoted by “CMD” in FIGS. 4 through 6 and FIG. 10 to be describedlater) at time t2 subsequent to time t1. The time period required tosend the command signal is T0 which is shorter than the time period Ts.When the sensor controller 31 has not yet detected the stylus 2, thesensor controller 31 sends the command signal that instructs the stylus2 to send a long burst signal. However, the stylus 2 which is above theuplink detection height AH is unable to receive the command signal anddoes not send a long burst signal in response to the command signal, butsimply repeats the detecting operation to detect the detection patternc1.

After the sensor controller 31 has sent the command signal thatinstructs the stylus 2 to send a long burst signal, the sensorcontroller 31 performs a detecting operation to detect a long burstsignal. This detecting operation corresponds to the first half of afull-range scanning process to be described later, and is carried outusing the N linear electrodes 30Y in succession. Details of thefull-range scanning process will be described later. Since the stylus 2does not send a long burst signal at this time, the sensor controller 31does not detect a long burst signal. The time period that can be usedfor the detecting operation to detect a long burst signal is T1 (Ts−T0)corresponding to the difference between the time period Ts and the timeperiod T0. When the detecting operation to detect a long burst signal isperformed using the N linear electrodes 30Y in succession, the detectingoperation of the long burst signal is temporarily completed at time t3,prior to time t4 (=t2+Ts) at which the time period T1 elapses. Thesensor controller 31 that has not detected a long burst signal duringthe detecting operation enters a sleep mode from time t3 to time t4. Thesensor controller 31 thus has its electric power consumption reduced.After time t4, the transmission of a pen trigger signal is repeated.

When the Stylus 2 is Within the Sensing Range SR and the SensorController 31 has not yet Identified the Position of the Stylus 2

FIG. 5(a) depicts the sequence in which the sensor controller 31 sends apen trigger signal, FIG. 5(b) depicts the sequence in which the sensorcontroller 31 receives a long burst signal sent by the stylus 2, usinglinear electrodes 30Y, and FIG. 5(c) depicts the sequence in which thesensor controller 31 receives a long burst signal sent by the stylus 2,using linear electrodes 30X.

As depicted in FIG. 5(a), when a pen-down movement is made (time t6),the stylus 2 can detect the detection pattern c1 in its subsequentdetecting operation (time t7) to detect the detection pattern c1. Havingdetected the detection pattern c1, the stylus 2 continues the detectingoperation until a delimiter pattern STP is detected. When the delimiterpattern STP is detected, the stylus 2 synchronizes with the sensorcontroller 31 on the basis of the detection time. The synchronization iscarried out by the generation of a transmission and reception scheduleto be specifically described later.

FIG. 5(a) depicts an example in which a pen-down movement is made attime t6 between time t5 at which a pen trigger signal starts being sentand time t8 (=t5+Ts) at which the pen trigger signal ends being sent,and the stylus 2 detects the detection pattern c1 at time t7 prior totime t8. The same process is carried out even if a pen-down movement ismade (e.g., at time t6′ depicted in FIG. 5(b)) while the sensorcontroller 31 is performing a detecting operation to detect a long burstsignal, except that the timing for the stylus 2 to detect the detectionpattern c1 is slightly delayed.

Then, as depicted in FIG. 5(b), when the sensor controller 31 startssending a command signal that instructs the stylus 2 to send a longburst signal at time t9 after time t8, the stylus 2 receives the commandsignal and continuously sends a long burst signal over a time period T1until time t10 (=t9+Ts). The sensor controller 31 detects the stylus 2by detecting the long burst signal thus sent.

Specifically, as depicted in FIG. 5(b), the sensor controller 31 usesthe N linear electrodes 30Y in succession to perform a detectingoperation to detect a long burst signal (the first half of a full-rangescanning process to be described later). At this time, since a longburst signal is detected with either one or more of the linearelectrodes 30Y, the sensor controller 31 stores the detected intensityof the long burst signal at each of the linear electrodes 30Y. Then, asdepicted in FIG. 5(c), the sensor controller 31 starts again to send acommand signal that instructs the stylus 2 to send a long burst signalat time t11 after time t10, and performs again a detecting operation todetect a long burst signal from the end of the transmission of thecommand signal. This detecting operation is carried out using the Mlinear electrodes 30X in succession until time t12 (=t11+Ts) (the latterhalf of a full-range scanning process to be described later). Since along burst signal is detected with either one or more of the linearelectrodes 30X in this detecting operation, the sensor controller 31stores the detected intensity of the long burst signal at each of thelinear electrodes 30X. The sensor controller 31 then derives thepositional coordinates of the stylus 2 on the touch surface on the basisof the previously stored detected intensity of the long burst signal ateach of the linear electrodes 30Y and the presently stored detectedintensity of the long burst signal at each of the linear electrodes 30X.

When the Stylus 2 is Within the Sensing Range SR and after the SensorController 31 has Identified the Position of the Stylus 2

FIG. 6 depicts the sequence in which the stylus 2 sends a burst signaland a data signal (data to be sent are not a unique ID) in hover state.Sequences of signals at the time the stylus 2 is in contact state and atthe time data to be sent is a unique ID will be described in detaillater.

As depicted in FIG. 6, the sensor controller 31 that has identified theposition of the stylus 2 starts sending a command signal that instructsthe stylus 2 to send data at subsequent time t13. In response to thecommand signal, the stylus 2 continuously sends a burst signal over timeperiod T4. The sensor controller 31 detects the burst signal, andderives positional coordinates of the stylus 2 on the basis of thedetected burst signal. The detecting operation to detect the burstsignal is carried out successively using only those of the M linearelectrodes 30X and the N linear electrodes 30Y which are indicated asbeing in the vicinity of the stylus 2 by the positional coordinates ofthe stylus 2 that have been derived at the last time (i.e. a sectorscanning process, to be described later). The stylus 2 sends a datasignal including data that it has been instructed to send, subsequentlyto the burst signal. The sensor controller 31 receives the data signaland decodes the data signal to acquire the data sent by the stylus 2.The reception of the data signal is carried out using only one linearelectrode 30X or linear electrode 30Y that corresponds to the positionalcoordinates of the stylus 2 that have been derived at the last time.

Referring back to FIG. 2, operation of the logic unit 70 at the time ofdetecting the stylus 2 and performing bidirectional communication withthe stylus 2 will be described in detail below with reference to FIG. 2.

For sending a pen trigger signal and a command signal that instructs thestylus 2 to send a long burst signal (FIGS. 4(a) and 4(b) and FIGS.5(a), 5(b) and 5(c)), the logic unit 70 controls the selector 40 to useall of the M linear electrodes 30X or all of the N linear electrodes 30Yor both of them simultaneously. Specifically, the logic unit 70 controlsthe selector 40 with the control signals sTRx, sTRy, selX, and selY sothat the output terminal of the transmitter 60 is connected to the Mlinear electrodes 30X or the N linear electrodes 30Y or both. Therefore,a pen trigger signal and a command signal that instructs the stylus 2 tosend a long burst signal are sent using the touch surface in itsentirety, thereby allowing the stylus 2 to receive these signals nomatter where it may be located in the sensing range SR depicted in FIG.1.

For receiving a long burst signal when the stylus 2 has not yet beendetected (FIG. 4(b) and FIG. 5(b)), the logic unit 70 controls theselector 40 to use the N linear electrodes 30Y in succession, asdepicted in FIG. 4(b) and FIG. 5(b). Specifically, the logic unit 70controls the selector 40 using the control signals sTRy and selY toconnect the N linear electrodes 30Y successively to the input terminalof the receiver 50. The sensor controller 31 can thus receive a longburst signal sent by the stylus 2, thereby detecting the stylus 2 nomatter where it may be located in the sensing range SR depicted in FIG.1.

FIG. 7(a) is a diagram illustrative of the manner in which the sensorcontroller 31 operates in such a case. As depicted in FIG. 7(a), thesensor controller 31 successively scans the N linear electrodes 30Y. Thesensor controller 31 does not scan the M linear electrodes 30X at thistime because it is possible to scan the entire surface of the sensor 30using only the N linear electrodes 30Y and, in addition, in order toincrease the scanning time period per electrode.

For receiving a long burst signal when positional coordinates of thestylus 2 have not yet been derived after having detected the stylus 2 byreceiving a long burst signal (FIG. 5(c)), the logic unit 70 controlsthe selector 40 to use the M linear electrodes 30X in succession, asdepicted in FIG. 5(c). Specifically, the logic unit 70 controls theselector 40 using the control signals sTRx and selX to connect the Mlinear electrodes 30X successively to the input terminal of the receiver50. The sensor controller 31 derives positional coordinates of thestylus 2 on the touch surface in the manner described above on the basisof the results of the control of the selector 40 and the previousdetection of the long burst signal with the N linear electrodes 30Y.

FIG. 7(b) is a diagram illustrative of the manner in which the sensorcontroller 31 operates in such a case. As depicted in FIG. 7(b), thesensor controller 31 successively scans the M linear electrodes 30X. Inthe present description, the scanning process that successively uses theN linear electrodes 30Y (the first half) as depicted in FIG. 7(a) andthe scanning process that successively uses the M linear electrodes 30X(the latter half) as depicted in FIG. 7(b) are combined together into aprocess referred to as “full-range scanning process.”

For sending a command signal after having derived positional coordinatesof the stylus 2 (FIG. 6), the logic unit 70 controls the selector 40 touse only those of the M linear electrodes 30X and the N linearelectrodes 30Y which are in the vicinity of the stylus 2. Specifically,if the stylus 2 is positioned at the intersection of the (j+5)th linearelectrode 30X and the (i+5)th linear electrode 30Y, for example, thenthe logic unit 70 controls the selector 40 using the control signalssTRx, sTRy, selX, and selY so that five linear electrodes, for example,on each of both sides of the intersection, i.e., the jth to (j+10)thlinear electrodes 30X and the ith to (i+10)th linear electrodes 30Y, aresimultaneously connected to the output terminal of the transmitter 60.Since the sensor controller 31 can now send a command signal using onlythose linear electrodes in the vicinity of the stylus 2, the electricpower consumption required to send a command signal is reduced. If thepalm of a hand or the like placed on the touch surface is supplied witha command signal, then the ground potential supplied to the stylus 2 mayincrease, possibly resulting in a reduction in the accuracy with whichthe stylus 2 detects an uplink signal. However, inasmuch the sensorcontroller 31 sends a command signal using only those linear electrodesin the vicinity of the stylus 2, as described above, the possibilitythat the palm of a hand or the like will be supplied with a commandsignal is low, and hence the accuracy with which the stylus 2 detects anuplink signal will not be lowered.

For receiving a normal burst signal rather than a long burst signalafter having derived positional coordinates of the stylus 2 (FIG. 6),the logic unit 70 controls the selector 40 to use only those of the Mlinear electrodes 30X and the N linear electrodes 30Y which are in thevicinity of the stylus 2. Specifically, if the stylus 2 is positioned atthe intersection of the (j+5)th linear electrode 30X and the (i+5)thlinear electrode 30Y, for example, then the logic unit 70 controls theselector 40 using the control signals sTRx, sTRy, selX, and selY so thatfive linear electrodes, for example, as depicted in FIG. 6, on each ofboth sides of the intersection, i.e., the jth to (j+10)th linearelectrodes 30X and the ith to (i+10)th linear electrodes 30Y, aresuccessively connected to the input terminal of the receiver 50. Sincethe reception time period per linear electrode is thus increased, it ispossible to receive a burst signal reliably.

FIG. 7(c) is a diagram illustrative of the manner in which the sensorcontroller 31 operates in such a case. In this example, it is assumedthat the stylus 2 is positioned at the intersection of the (j+5)thlinear electrode 30X and the (i+5)th linear electrode 30Y. The sensorcontroller 31 successively scans only 11 linear electrodes 30X rangingfrom the jth to (j+10)th linear electrodes 30X and 11 linear electrodes30Y ranging from the ith to (i+10)th linear electrodes 30Y, among theM×N linear electrodes, and derives positional coordinates of the stylus2 on the basis of the results of the scanning process. The scanningprocess in which both of some of the M linear electrodes X and some ofthe N linear electrodes Y are used to re-derive (update) positionalcoordinates of the stylus 2 that have been derived once is referred toas “sector scanning process.”

For receiving a data signal (FIG. 6), the logic unit 70 controls theselector 40 to use only one linear electrode 30X or linear electrode 30Ycorresponding to the position of the stylus 2 derived from the lastburst signal. Specifically, the logic unit 70 controls the selector 40using the control signals sTRx, sTRy, selX, and selY so that one linearelectrode 30X or linear electrode 30Y is connected to the input terminalof the receiver 50. It is now possible to utilize the data signaltransmission time period (=T1−T4) to the fullest for the purpose ofsending data from the stylus 2 to the sensor controller 31.

The operation of the logic unit 70 for detecting the stylus 2 andperforming bidirectional communication with the stylus 2 has beendescribed above.

FIG. 8 is a block diagram depicting functional blocks of the stylus 2according to the present embodiment. As depicted in FIG. 8, the stylus 2includes a core body 20, an electrode 21, a switch 22, a pen pressuredetection sensor 23 (pen pressure detector), and a signal processor 24.

The core body 20 is an insulative member serving as a pen tip of thestylus 2. The electrode 21 is a conductive member provided adjacent tothe core body 20 (particularly in the vicinity of the distal endthereof). The electrode 21 serves as an antenna that sends downlinksignals and also as an antenna for receiving uplink signals sent fromthe sensor controller 31 via the capacitive coupling. An electrode thatsends downlink signals and an electrode for receiving uplink signals maybe combined as one electrode or may be separate from each other.

The switch 22 includes a switch that can be turned on or off by theuser, and may be a side switch mounted on a side surface of the stylus 2or a tail switch mounted on a rear end of the stylus 2. The pen pressuredetection sensor 23 is a pressure sensor for detecting a pressure (penpressure) applied to the distal end of the core body 20.

The signal processor 24 has a function to receive uplink signals fromthe sensor controller 31 via the electrode 21, perform processingsequences depending on the contents of the received uplink signals,generate downlink signals to be sent to the sensor controller 31, andsend the generated downlink signals to the sensor controller 31 via theelectrode 21. Specifically, the signal processor 24 functionallyincludes a switch 76, a receiver 71, a transmitter 75, and a controller90. These functional blocks will be described below in order.

The switch 76 includes a one-circuit two-contact switch element where acommon terminal is selectively connected to either one of T terminal andR terminal. The common terminal of the switch 76 is connected to theelectrode 21, T terminal thereof is connected to the output terminal ofthe transmitter 75, and R terminal thereof is connected to the inputterminal of the receiver 71. The state of the switch 76 is controlled bycontrol signals SWC from the controller 90. For receiving uplink signalsfrom the sensor controller 31, the controller 90 controls the switch 76with the control signal SWC so that R terminal and the common terminalare connected to each other. For sending downlink signals to the sensorcontroller 31, the controller 90 controls the switch 76 with the controlsignal SWC so that T terminal and the common terminal are connected toeach other. In an initial state, i.e., during a period until the stylus2 detects the detection pattern cl described above, the controller 90controls the switch 76 to keep R terminal and the common terminalconnected to each other, and then enters a sleep mode for reducing theelectric power consumed by the stylus 2.

The receiver 71 is a circuit that receives a signal supplied from theswitch 76 (a signal that has reached the electrode 21) and decodes thesymbol values contained in the received signal. The receiver 71 includesa waveform regenerator 71 a and a correlation operator 71 b. Thereceiver 71 is arranged to be able to detect a detection pattern c1, adelimiter pattern STP, and control information c2 described above bydecoding the symbol values. Until the receiver 71 detects a detectionpattern c1, it performs its receiving operation only intermittently inorder to reduce the electric power consumed by the stylus 2.

The waveform regenerator 71 a binarizes the level of an electric charge(voltage) induced in the electrode 21 with a clock that is several times(e.g., four times) the chip rate of the spread code PN described above,shapes the binarized level into a binary train (chip train) havingpositive and negative polarity values, and outputs the chip train. Thecorrelation operator 71 b stores the chip train output from the waveformregenerator 71 a into a register, performs a correlation operation onthe chip train while successively shifting it with the above clock withrespect to the spread code PN (or a code produced by inverting and/orcyclically shifting the spread code PN), thereby decoding the symbolvalues contained in the received signal.

The receiver 71 sequentially determines whether the symbol valuesdecoded by the correlation operator 71 b represent the detection patterncl or not. If the receiver 71 detects the detection pattern c1 as aresult, then the receiver 71 detects the existence of the sensorcontroller 31 and issues a trigger signal EN, which makes it possible toperform a process depending on the command represented by the commandsignal, to the controller 90.

When the receiver 71 has detected the detection pattern c1, it switchesfrom the intermittent receiving operation to a continuous receivingoperation, and sequentially determines whether the decoded symbol valuesrepresent the delimiter pattern STP or not. If the receiver 71 detectsthe delimiter pattern STP as a result, then the receiver 71 outputsdetection time t2 to the controller 90.

After having detected the delimiter pattern STP, the receiver 71performs a receiving operation to receive a command signal sent by thesensor controller 31 according to a schedule (to be described later)from the controller 90. Specifically, the receiver 71 acquires a stringof symbol values decoded by the correlation operator 71 b during thereceiving operation, as control information c2, and outputs the acquiredcontrol information c2 to the controller 90.

The controller 90, which includes a microprocessor (MCU), is activatedupon the supply of a trigger signal EN from the receiver 71, andgenerates a transmission and reception schedule for various signals onthe basis of detection time t2 supplied from the receiver 71. Then, thecontroller 90 performs a process of generating control signals SWC basedon the generated transmission and reception schedule and supplying thegenerated control signals SWC to the switch 76, a process of controllingthe receiver 71 to receive command signals, and a process of controllingthe transmitter 75 on the basis of control information c2 supplied fromthe receiver 71.

The process performed by the controller 90 to control the transmitter 75includes determining the kind of a signal (either one of signals (A)through (F) depicted in FIG. 10 to be described later) to be sent to thesensor controller 31 on the basis of a received command signal. If adata signal representing certain data is to be sent, the controller 90acquires data which it is instructed to send by control information c2and supplies the acquired data to the transmitter 75. The data suppliedto the transmitter 75 include a unique ID of the stylus 2 which isstored in a memory, not depicted, data indicating whether the switch 22is turned on or off, and data representing the pen pressure detected bythe pen pressure detection sensor 23, etc.

For controlling the transmitter 75 to send a data signal, the controller90 determines whether the stylus 2 is in contact state or in hoverstate, and performs a process of controlling a bit rate depending on theresult of the determination. Specifically, if the result of thedetermination indicates a contact state, then the controller 90 controlsthe transmitter 75 to send at least part of the data to be sent at afirst bit rate, and if the result of the determination indicates a hoverstate, then the controller 90 controls the transmitter 75 to send atleast part of the data to be sent at a second bit rate that is lower(smaller) than the first bit rate. This process will be described ingreater detail later.

The transmitter 75 is a circuit that generates signals to be sent to thesensor controller 31 and supplies the generated signals to the electrode21, and includes a modulator 73 and a voltage boosting circuit 74. Thetransmitter 75 supplies signals to be sent to the electrode 21, tothereby perform a process of sending the signals including data to besent using the electrode 21.

The modulator 73 is a circuit that generates a carrier signal (e.g., arectangular-wave signal) having a predetermined frequency or a frequencycontrolled by the controller 90, and outputs the carrier signal as it isor after modulating it under the control of the controller 90. When along burst signal or a burst signal is to be sent, the modulator 73 doesnot modulate the carrier signal and outputs the carrier signal as it is,or modulates the carrier signal with a pattern of known values sharedwith the sensor controller 31 and outputs the modulated carrier signal.In this manner, the modulator 73 outputs a long burst signal prior tobeing boosted or outputs a burst signal prior to being boosted. When adata signal is to be sent, the modulator 73 modulates the carrier signalwith data supplied from the controller 90 (by way of on/off keying(OOK), phase shift keying (PSK), or the like), and outputs the modulatedsignal obtained as a result. In this manner, the modulator 73 outputs adata signal prior to being boosted.

The voltage boosting circuit 74 is a circuit that boosts the voltage ofoutput signals from the modulator 73 to a certain amplitude, to therebygenerate a long burst signal, a burst signal, and a data signal. Thelong burst signal, the burst signal, and the data signal that have beengenerated by the voltage boosting circuit 74 are supplied via the switch76 to the electrode 21, from which they are transmitted into space.

The outline of the arrangements and the operation of the stylus 2 andthe sensor controller 31 according to the present embodiment has beendescribed above with reference to FIGS. 1 through 8. Now, operation ofthe stylus 2 and the sensor controller 31 related to the features of thepresent disclosure will be described in detail below with reference toFIGS. 9 through 19.

FIG. 9 is a flowchart of an overall processing sequence that the sensorcontroller 31 performs. In FIG. 9, however, only the processing sequenceat the time the stylus 2 is in hover state is illustrated by way ofexample. As depicted in FIG. 9, the sensor controller 31 is arranged torepeat the same operation in each time period Tr (e.g., 16.67 ms whichis a reciprocal of 60 Hz), which is defined as the reciprocal of adisplay refresh rate of a display panel disposed together with thesensor 30.

In each periodic cycle, the sensor controller 31 first determineswhether it has requested the stylus 2 to send a unique ID or not (stepS1). The request is made by sending a command signal that instructs thestylus 2 to send a unique ID.

If the sensor controller 31 determines that it has not requested thestylus 2 in step S1, then the sensor controller 31 performs a stylusdetecting process (step S2 a) and a finger touch detecting process(steps S3 and S4) alternately each for four times. Each stylus detectingprocess is continuously carried out over a time period Ts (2500 μs, forexample, which is the same as the time period Ts depicted in FIGS. 4through 6), and each finger touch detecting process is continuouslycarried out over a time period Tf (e.g. 1500 μs). For detecting fingerF, two finger touch detecting processes (step S3 and step S4) that areperformed separately before and after a stylus detecting process arecarried out as a single finger touch position detecting unit.

If the sensor controller 31 determines that it has requested the stylus2 in step S1, then the sensor controller 31 performs a stylus detectingprocess (step S2 b) repeatedly for four times. Each stylus detectingprocess is continuously carried out over a time period Ts+Tf. Since nofinger touch detecting process is carried out, no input with from fingerF depicted in FIG. 1(a) is possible while the stylus detecting processis repeatedly performed. The time period over which the stylus detectingprocess is continued is increased while limiting input with finger Fbecause the size of a unique ID is so large that a long period of timeis needed to send the entire unique ID from the stylus 2 to the sensorcontroller 31. A unique ID may be sent once per pen-down movement, andit is considered that a user typically does not make an input withfinger F at the same time as a pen-down movement of the stylus 2.Furthermore, the restrictive time period continues for only the timeperiod Tr (e.g., 16.67 ms). For these reasons, the restriction on inputwith finger F in favor of the transmission of a unique ID is consideredto not adversely affect the user's usage of the sensor.

Hereinafter, each periodic cycle commensurate with the time period Ts+Tfwill be referred to as “frame,” and each periodic cycle commensuratewith the time period Tr (operational periodic cycle of a display processof the display panel) will be referred to as “superframe.” In otherwords, the stylus 2 according to the present embodiment sends downlinksignals in the unit of a superframe, and also in the unit of a frame. Inthe example depicted in FIG. 9, one superframe includes four frames.However, the number of frames included in one superframe is not limitedto four. A “frame” and a “superframe” including a plurality of framesmay be rephrased as a “packet” and a “frame” including a plurality ofpackets, respectively.

FIG. 10 is a diagram depicting a format of downlink signals that aresent by the stylus 2 while the sensor controller 31 is performing stylusdetecting processes. As described above, the downlink signals include along burst signal, a burst signal, and a data signal. FIG. 10 depictsfive types of data (A) through (E) as data sent by the data signal. Forthe sake of brevity, the transmission of a data signal may be referredto as “transmission of data” below.

Data (D) and (E) depicted hatched with lines slanting down to the rightin FIG. 10 are sent while the stylus 2 is in contact state, and are sentby the stylus 2 at the first bit rate. Data (B) and (C) are sent whilethe stylus 2 is in hover state, and are sent by the stylus 2 at thesecond bit rate that is smaller than the first bit rate. Data (A) issent regardless of whether the stylus 2 is in hover state or in contactstate, and is sent by the stylus 2 at the second bit rate. The presentdisclosure is primarily characterized in that the bit rates of data (A)through (E) are controlled in this manner.

Details of operation of the sensor controller 31 and the stylus 2 willbe described below with reference to FIG. 10 and flowcharts ofprocessing sequences of the sensor controller 31 and the stylus 2.

FIG. 11 is a flowchart of a process of receiving uplink signals and aprocess of sending downlink signals, which are carried out by the stylus2. Operation of various components (particularly, the receiver 71, thetransmitter 75, and the controller 90) of the stylus 2 depicted in FIG.8 will be described in detail below with reference to FIG. 11.

Although not depicted, the controller 90 of the stylus 2 stores thereina state flag that indicates its own states. The states that can beindicated by the state flag include a sensor controller undetected state(=0) and a sensor controller detected state (=1). The controller 90refers to the state flag (step S70) at the start timing of a framedescribed above, and controls the transmitter 75 to send signals in eachframe.

If the state flag referred to in step S70 indicates “0,” then thereceiver 71 of the stylus 2 enters a receiving operation disabled state(step S71). After a predetermined time period has elapsed, the receiver71 tries to detect a detection pattern c1 described above (step S72).The disabled period is provided in step S71 in order to reduce theelectric power consumed by the stylus 2 by intermittently performing thedetecting operation to detect a detection pattern c1.

Then, the receiver 71 determines whether a detection pattern cl has beendetected by the detecting operation tried in step S72 (step S73). If thereceiver 71 determines that a detection pattern c1 has not been detectedas a result, then control goes back to step S70. If the receiver 71determines that a detection pattern c1 has been detected, then thereceiver 71 issues a trigger signal EN depicted in FIG. 8 to activatethe controller 90, and continues a detecting operation to detect symbolsof a detection pattern c1 and a delimiter pattern STP until a delimiterpattern STP is detected (step S74). If a delimiter pattern STP isdetected, then the receivers 71 outputs detection time t2 (FIG. 8) tothe controller 90. In response to detection time t2, the controller 90performs a process of synchronizing with the sensor controller 31(specifically, a process of generating a transmission and receptionschedule described above) on the basis of detection time t2 (step S75),and sets the state flag to “1” (step S76), after which control goes backto step S70.

If the state flag referred to in step S70 indicates “1,” then thecontroller 90 performs a detecting operation to detect a command signal(step S80). The detecting operation is specifically an operation inwhich the controller 90 is supplied with control information c2 (FIG. 8)from the receiver 71, and is carried out over the time period T0 (e.g.,200 μs) depicted in FIGS. 4 through 6. Then, the controller 90determines whether a command signal has been detected by the detectingoperation in step S80 (step S81). If the controller 90 determines that acommand signal has not been detected, then the controller 90 sets thestate flag to “0” (step S82), after which control goes back to step S70.Step S82 indicates a process in which the stylus 2 fails to detectuplink signals for the reason that the stylus 2 has moved out of theuplink detection height AH depicted in FIG. 1, for example.

If the controller 90 determines that a command signal has been detectedin step S81, then the controller 90 determines the content of thedetected command signal (the content of a command from the sensorcontroller 31) (step S83). Specifically, the content of the commandsignal indicates a command (LB) to send a long burst signal, a command(ID) to send a unique ID, or a command (DT) to send data other than aunique ID.

If the controller 90 determines that the content of the command signalindicates a command (LB) to send a long burst signal in step S83, thenthe controller 90 controls the transmitter 75 to send a long burstsignal (step S84). More specifically, the controller 90 controls thetransmitter 75 to send a long burst signal over a time period T1 fromtime t1 to time t5 after having received the command signal sent over atime period T0 from time t0 to time t1, as depicted at (1) in FIG. 10.As described above with reference to FIG. 4, T1=Ts−T0. Thereafter, thecontroller 90 returns control to step S70, as depicted in FIG. 11.

If the controller 90 determines that the content of the command signalindicates a command (ID) to send a unique ID in step S83, then thecontroller 90 determines whether the stylus 2 is in hover state or not(step S85). This determining process is carried out by referring to thepen pressure that is being detected by the pen pressure detection sensor23 depicted in FIG. 8. Specifically, the controller 90 determines thatthe stylus 2 is in hover state if the pen pressure that is beingdetected by the pen pressure detection sensor 23 is zero, and determinesthat the stylus 2 is not in hover state (the stylus 2 is in contactstate) if the pen pressure that is being detected by the pen pressuredetection sensor 23 is larger than zero.

If the controller 90 determines that the stylus 2 is in hover state instep S85, then the controller 90 controls the transmitter 75 to send aburst signal (step S86) and then send data (A) and data (B) according toa second transmission process (steps S87 and S88).

As depicted at (2) in FIG. 10, data (A) includes data including a burstsignal, a predetermined start flag Start, and state information Stateincluding 1-bit information that indicates the result of thedetermination (the hover state or the contact state) in step S85. Inthis case, the state information State indicates the hover state. Thecontroller 90 controls the transmitter 75 to send the burst signal overa time period T4 from time t1 to time t2 (see FIG. 3) and, thereafter,send the start flag Start and the state information State successivelyin this order until subsequent time t3 according to the secondtransmission process. The second transmission process is a method ofsending each bit at the second bit rate described above. For sendingeach bit, the second transmission process uses a second time period(e.g., 90 μs) longer than a first time period (e.g., 30 μs) used in afirst transmission process to be described later. A gap time periodhaving a predetermined time length is inserted between the burst signaland the start flag Start.

As depicted at (2) in FIG. 10, data (B) includes data including modeinformation Mode, a frame index number FN, part of a unique ID, and acheck sum CS. The controller 90 controls the transmitter 75 to sendthese items of information in this order according to the secondtransmission process as with data (A) immediately after time t3 when thetransmission of the state information State is finished until time t7where the frame ends. With data (B) being thus sent, the time periodrequired from the start of reception of the command signal until the endof the transmission of data (B) is represented by Ts+Tf, which fails toprovide time periods for detecting a finger touch as depicted in FIG. 9.In this case, therefore, the sensor controller 31 is unable to detect afinger touch.

The components of data (B) will be described in detail. The modeinformation Mode is 1-bit information indicating the type of data (aunique ID or other data) that is about to be sent. In data (B), the typeof data indicated by the mode information Mode is “unique ID.”

The frame index number FN is 2-bit information indicating the order offrames in a superframe, and indicates which frame in one superframe thepresently performed stylus detecting process belongs to.

The unique ID is 52-bit information that differs from stylus to stylus.The 52-bit information is information that is very large in size forinformation to be sent by the stylus 2, and cannot be fully sent in oneframe. Therefore, it is divided among the frames in one superframe andthen sent. Specifically, the unique ID is divided into units of 13 bitseach and sent on all four frames in one superframe. The frame indexnumber FN is used for the sensor controller 31 to recover the unique IDthat has been sent as divided pieces.

Inverted bits Op are placed among and immediately after the unique ID.Each of the inverted bits Op includes a bit that is generated byinverting the last one of a predetermined number of bits. The controller90 controls the transmitter 75 to send an inverted bit Op immediatelyafter this predetermined number of bits. In the example depicted at (2)in FIG. 10, one inverted bit Op is placed immediately after 6 bits ofthe unique ID and one inverted bit Op is placed immediately after 7subsequent bits of the unique ID. An inverted bit Op is added to preventmore than a predetermined number of identical bits from continuing.

The check sum CS is an error detecting code calculated on the basis ofdata (e.g., 13 bits of the unique ID) included in the same data (B).Though the number of bits of the check sum CS is arbitrary, it isillustrated as 3 in FIG. 10. The controller 90 calculates a check sum CSwhen generating data (B), for example, and places the calculated checksum CS at the end of data (B). The sensor controller 31 calculates acheck sum CS on its own after it has received the unique ID, andcompares it with the received check sum CS to determine whether theunique ID has been received correctly or not.

Referring back to FIG. 11, if the controller 90 determines that thestylus 2 is in contact state in step S85, then the controller 90controls the transmitter 75 to send a burst signal (step S89), then senddata (A) according to the second transmission process (step S90), andsubsequently send data (D) according to the first transmission process(step S91).

The content of data (A) is configured as described above. However, thestate information State in this case indicates the contact state.

As depicted at (5) in FIG. 10, data (D) is a signal including modeinformation Mode, a frame index number FN, part of a unique ID, and acheck sum CS. The type indicated by the mode information Mode is “uniqueID.” Data (D) includes inverted bits Op inserted in a total of threelocations, i.e., at the start of data (D) and two locations in theunique ID (more specifically, immediately after 3 bits of the unique IDand immediately after 6 subsequent bits of the unique ID).

The number of bits of the unique ID sent with one item of data (D) is12. The check sum CS is a 3-bit error detecting code calculated on thebasis of 12 bits of the unique ID included in the same data (D), forexample. As is the case with data (B), the unique ID is divided amongand sent on all four frames in one superframe. However, since the totalnumber of bits of the unique ID is 52 as described above, when 12 bitsare assigned per frame, there occurs a shortage of 4 bits. 4 bits of theunique ID will be sent as a serial number SN in data (E) to be describedlater.

The controller 90 controls the transmitter 75 to send the respectiveitems of information of data (D) in the above-described order accordingto the first transmission process immediately after time t3 when thetransmission of the state information State is finished until time t6.The first transmission process is a method of sending each bit at thefirst bit rate described above. For sending each bit, the firsttransmission process uses a first time period of 30 μs, for example. Thetime length of 30 μs is ⅓ of the second time period used in the secondtransmission process. Time t6 is slightly later than time t5 (earlierthan time t7 when the frame ends) at which the stylus detecting processends when sending a long burst signal. A time period T3 (=t6−t1)required to send the burst signal, data (A), and data (D) is slightlylonger than the time period T1 required to send the long burst signal.With data (D) being thus sent, although part of the time period fordetecting a finger touch as depicted in FIG. 9 is consumed in thetransmission and reception of data (D), the time period for detecting afinger touch is encroached on only slightly, so that the sensorcontroller 31 is able to detect a finger touch.

Referring back to FIG. 11, if the controller 90 determines that thecontent of the command signal indicates a command (DT) to send dataother than a unique ID in step S83, then the controller 90 determineswhether the stylus 2 is in hover state or not (step S92). The details ofthe determination in step S92 are the same as those in step S85, andwill not be described below.

If the controller 90 determines that the stylus 2 is in hover state instep S92, then the controller 90 controls the transmitter 75 to send aburst signal (step S93) and then send data (A) and data (C)consecutively according to the second transmission process (steps S94and S95).

The content of data (A) is configured as described above. However, thestate information State in this case indicates the hover state.

As depicted at (3) in FIG. 10, data (C) is a signal including modeinformation Mode, two items of switch information SW1 and SW2, andbattery information Bat. Alternatively, as depicted at (4) in FIG. 10,data (C) is a signal including only mode information Mode. In this case,the type of data indicated by the mode information Mode is “other data.”The first item of switch information SW1 is 1-bit information indicatingwhether the switch 22 depicted in FIG. 8 is turned on or off (firstdigital value). As can be understood from (3) in FIG. 10, the stateinformation State is placed before the switch information SW1 in oneframe. According to the present embodiment, the second item of switchinformation SW2 is kept in reserve and is not actually used. The batteryinformation Bat is 1-bit information indicating the available amount ofelectric energy stored in a cell (not depicted) for energizing thestylus 2. The battery information Bat indicates the available amount ofelectric energy stored in the cell by way of how often the bit becomes“1” in a plurality of transmission events.

The controller 90 controls the transmitter 75 to send data (C) depictedat (3) in FIG. 10 in the first and third frames in one superframe, andcontrols the transmitter 75 to send data (C) depicted at (4) in FIG. 10in the second and fourth frames in one superframe. The content of datato be sent is thus varied depending on the frame because priority isgiven to the reduction of the electric power consumed by the stylus 2 inview of the fact that there is no need to send the switch informationSW1 and SW2 and the battery information Bat at a high rate.

With respect to data (C) depicted at (3) in FIG. 10, the controller 90controls the transmitter 75 to send the items of information making updata (C) in the order described above according to the secondtransmission process immediately after time t3 when the transmission ofthe state information State is finished until time t5. Therefore, thetime period required to send the burst signal, data (A), and data (C) isT1 that is the same as the time period required to send a long burstsignal. With respect to data (C) depicted at (4) in FIG. 10, thecontroller 90 controls the transmitter 75 to send the mode informationMode of data (C) according to the second transmission processimmediately after time t3 when the transmission of the state informationState is finished until time t4 (between time t3 and time t5). In thelatter case, the controller 90 is in a sleep mode during a time periodfrom time t4 to time t5, reducing as much electric power consumed by thestylus 2.

Referring back to FIG. 11, if the controller 90 determines that thestylus 2 is in contact state in step S92, then the controller 90controls the transmitter 75 to send a burst signal (step S97), then senddata (A) according to the second transmission process (step S98), andfurther send data (E) according to the first transmission process (stepS99).

The content of data (A) is configured as described above. However, thestate information State in this case indicates the contact state.

As depicted at (6) in FIG. 10, data (E) is a signal including modeinformation Mode, a frame index number FN, a serial number SN, reservedinformation RS, pen pressure data P, switch information SW1, and a checksum CS. In this case, the type of data indicated by the mode informationMode is “other data.” Data (E) includes inverted bits Op inserted in atotal of three locations, i.e., at the start of data (E), immediatelyafter the reserved information RS, and immediately after the penpressure data P.

The serial number SN is represented by 4 bits of information out of the52 bits of the unique ID, as described above, and is used for the sensorcontroller 31 to identify a plurality of styluses 2 which are in usewith the same sensor controller 31. The serial number SN may includeinformation that specifies a pen tip setting type representing thesetting state of the pen tip of the stylus 2 (pencil, brush, etc.). Aswith the unique ID, the serial number SN is divided into units of 1 biteach and sent on all four frames in one superframe. The sensorcontroller 31 stores 48 bits received from data (D) and couples themwith 4 bits received from data (E), obtaining the entire unique ID.

The reserved information RS is information that the vender of the stylus2 can set freely, and 2 bits are reserved therefor.

The pen pressure data P includes 12 bits of data indicating a penpressure detected by the pen pressure detection sensor 23 (seconddigital value), and is divided into units of 6 bits each that are placedin two consecutive frames (specifically, the first and second frames orthe third and fourth frames in one superframe).

The controller 90 controls the transmitter 75 to send the items ofinformation of data (E) in the above-described order according to thefirst transmission process immediately after time t3 when thetransmission of the state information State is finished until time t6.Therefore, part of the time period for detecting a finger touch asdepicted in FIG. 9 is consumed in the transmission and reception of data(E). However, as with data (D), since the time period for detecting afinger touch is encroached on only slightly, the sensor controller 31 isable to detect a finger touch.

As described above, the controller 90 controls the transmitter 75 toselectively send data (A) through (E) depending on commands from thesensor controller 31, and at the same time also controls their bit ratesdepending on the state of the stylus 2 (the contact state or the hoverstate). Specifically, the controller 90 makes the bit rate of data (B)and (C) sent in hover state (the second bit rate described above)smaller than the bit rate of data (D) and (E) sent in contact state (thefirst bit rate described above). The controller 90 also controls thetransmitter 75 to send data (A) at the second bit rate as with data (B)and (C) sent in hover state. FIG. 10 depicts an example in which theratio of the first bit rate and the second bit rate is 3:1. However, theratio can be changed appropriately. The controller 90 performs such bitrate control in order to improve the noise resistance in hover state inwhich the S/N ratio of downlink signals tends to be poor and also toallow the sensor controller 31 to receive the state information Statereliably particularly with respect to data (A). These aspects will bedescribed again in detail later.

FIGS. 12 and 13 are flowcharts of a process of sending uplink signalsand a process of receiving downlink signals, which are carried out bythe sensor controller 31. The processes of the sensor controller 31 thatcorrespond to the process of the stylus 2 which is depicted in FIG. 11will be described below with reference to FIGS. 12 and 13.

As with the stylus 2, the sensor controller 31 stores therein a stateflag that indicates its own states. The states that can be indicated bythe state flag include a stylus undetected and pen trigger signaltransmission waiting state (=0), a stylus undetected and response to apen trigger signal waiting state (=1), a stylus detected and positionunderived state (=2), a stylus position derived and unique ID unreceivedstate (=3), and a unique ID received state (=4). The sensor controller31 initially refers to the state flag (step S10).

If the state flag referred to in step S10 indicates “0,” then the sensorcontroller 31 sends a pen trigger signal over a time period Ts depictedin FIG. 9, etc. (step S11). Specifically, the sensor controller 31 sendsa repetition of a detection pattern c1 and a delimiter pattern STP.Having finished the continuous transmission of the pen trigger signal,the sensor controller 31 performs a process of detecting a finger touchover a time period Tf in FIG. 9, etc. (step S12) and sets the state flagto “1” (step S13), after which control goes back to step S10. In FIG.12, step S12 is followed by step S13. However, these steps may becarried out in parallel to each other. This relationship also holds truefor other finger touch detecting processes (steps S16, S23, S41, S54 andS61) to be described later and subsequent processes (e.g., steps S17through S20 with respect to step S16).

If the state flag referred to in step S10 indicates “1,” then the sensorcontroller 31 sends a command signal that instructs the stylus 2 to senda long burst signal (requesting LB) (step S14). The transmission ofvarious command signals including this command signal takes the timeperiod T0 described above. Thereafter, the sensor controller 31 performsa receiving operation to receive a long burst signal depicted in FIG. 10over the time period T1 described above (step S15). This receivingoperation is performed in the first half of the full-range scanningprocess described with reference to FIG. 7(a).

When the time period T1 has elapsed and the receiving operation toreceive a long burst signal is finished, the sensor controller 31performs a process of detecting a finger touch over a time period Tf(step S16) and determines whether it has received a long burst signal ornot (step S17). If the sensor controller 31 determines that it has notreceived a long burst signal as a result, then it sets the state flag to“0” (step S18), after which control goes back to step S10. Step S18indicates a process in which the sensor controller 31 fails to detectdownlink signals for the reason that the stylus 2 is outside the sensingrange SR depicted in FIG. 1, for example. If the sensor controller 31determines that it has received a long burst signal in step S17, then itsets the state flag to “2” (step S19) and determines a command to besent to the stylus (step S20), after which control goes back to stepS10. The command that is determined here is a command (LB) thatinstructs the stylus 2 to send a long burst signal.

If the state flag referred to in step S10 indicates “2,” then the sensorcontroller 31 sends again a command signal that instructs the stylus 2to send a long burst signal (requesting LB) (step S21). Thereafter, thesensor controller 31 performs a receiving operation to receive a longburst signal over the time period T1 (step S22). This receivingoperation is performed in the latter half of the full-range scanningprocess described with reference to FIG. 7(b). When the operation of thefirst half of the full-range scanning process (step S15) and theoperation of the latter half of the full-range scanning process (stepS22) can be carried out in one time period T1, these two steps S15 andS22 may be performed in one process.

When the time period T1 has elapsed and the receiving operation toreceive a long burst signal is finished, the sensor controller 31performs a process of detecting a finger touch over a time period Tf(step S23) and determines whether it has received a long burst signal ornot (step S24). If the sensor controller 31 determines that it has notreceived a long burst signal as a result, then it sets the state flag to“0” (step S25), after which control goes back to step S10. Step S25indicates a process in which the sensor controller 31 fails to detectdownlink signals for the reason that the stylus 2 has left the sensingrange SR depicted in FIG. 1, for example. If the sensor controller 31determines that it has received a long burst signal in step S24, then itsets the state flag to “3” (step S26) and derives the position of thestylus 2 on the basis of the result of the detection of the long burstsignal in step S15 and the result of the detection of the long burstsignal in step S22 (step S27). The sensor controller 31 then determinesa command to be sent to the stylus (step S28), after which control goesback to step S10. The command that is determined here is a command(requesting ID) that instructs the stylus 2 to send a unique ID and thatalso serves to instruct the stylus 2 to send an ordinary burst signal asopposed to a long burst signal. A command to be sent in step S50 to bedescribed later (a command (requesting DT) that instructs the stylus 2to send data other than a unique ID) also serves to instruct the stylus2 to send a burst signal.

If the state flag referred to in step S10 indicates “3,” then the sensorcontroller 31 sends a command signal representing a command determinedin step S28 or step S37 or S45 to be described later (step S30).Thereafter, the sensor controller 31 successively performs receivingoperations to receive a burst signal and data (A) (steps S31 a and S31b). When the sensor controller 31 receives a burst signal, it derivespositional coordinates of the stylus 2 on the basis of the detectedintensities of the received burst signal at the linear electrodes 30Xand 30Y.

The receiving operation to receive a burst signal in step S31 a isperformed according to the sector scanning process described withreference to FIG. 7(c). The receiving operation to receive data (A) instep S31 b is carried out using one linear electrode 30X or linearelectrode 30Y selected on the basis of the positional coordinatesderived from the detected intensities of the burst signal. The sensorcontroller 31 acquires data (A) by demodulating the received signalaccording to a first demodulation process corresponding to the secondbit rate described above. These details also apply to the detection of aburst signal and data (A) in steps S51 a and S51 b to be describedlater.

Having finished the receiving operations to receive a burst signal anddata (A), the sensor controller 31 determines whether the stylus 2 is inhover state or not by confirming the state information State included indata (A) (step S32). If the sensor controller 31 determines that thestylus 2 is in hover state, then the sensor controller 31 performs areceiving operation to receive data (B) (step S33). As described abovewith reference to FIG. 10, since the transmission of data (B) continuesuntil the time at which the frame ends, the sensor controller 31 doesnot perform a process of detecting a finger touch.

As with the receiving operation to receive data (A), the receivingoperation in step S33 is carried out using one linear electrode 30X orlinear electrode 30Y selected on the basis of the positional coordinatesderived in step S31. This also holds true for receiving operations toreceive data (C) through (E) to be described later (steps S40, S53, andS60). In this manner, it is possible to utilize the time period fordetecting data signal to the fullest, so that the sensor controller 31can send more data to the stylus 2. The sensor controller 31 acquiresdata (B) by demodulating the received signal according to the firstdemodulation process described above. This also applies to the receivingoperation to receive data (D) to be described later (step S53).

Having finished the receiving operation to receive data (B), the sensorcontroller 31 determines whether it has received a burst signal, data(A), or data (B) or not (step S34). If the sensor controller 31determines that it has not received any of them as a result, it sets thestate flag to “0” (step S35), after which control returns to step S10.Step S35 indicates a process in which the sensor controller 31 fails todetect downlink signals for the reason that the stylus 2 has left thesensing range SR depicted in FIG. 1, for example. If the sensorcontroller 31 determines that it has received any one of them in stepS34, then the sensor controller 31 determines whether it has receivedall (52 bits) of the fragments (13-bit data) of a unique ID that can bereceived via data (B) or not (step S36). If the sensor controller 31determines that there are some fragments (remaining data) not yetreceived, then it determines a command that instructs the stylus 2 tosend a unique ID (requesting ID) as a command to be sent to the stylus 2(step S37), after which control goes back to step S10. If the sensorcontroller 31 determines that it has received all of the fragments (noremaining data) in step S36, then it sets the state flag to “4” (stepS38). The sensor controller 31 determines a command that instructs thestylus 2 to send data other than a unique ID (requesting DT) as acommand to be sent to the stylus 2 (step S39), and then returns controlto step S10.

Although not depicted, the sensor controller 31 then combines thereceived fragments of a unique ID, to thereby recover the unique ID andstore the recovered unique ID, in parallel to the execution of stepsS38, S39. In this case, the sensor controller 31 determines the order inwhich to combine the fragments on the basis of frame index numbers FNsent with the fragments.

If the sensor controller 31 determines that the stylus 2 is not in hoverstate (is in contact state) in step S32, then the sensor controller 31performs a receiving operation to receive data (D) (step S40). Asdepicted in FIG. 13, the receiving operation is carried out in a mannerto encroach slightly on the time period reserved for detecting a fingertouch. The sensor controller 31 carries out a process of detecting afinger touch using a time period remaining after step S40 (step S41).The sensor controller 31 acquires data (D) by demodulating the receivedsignal according to a second demodulation process corresponding to thefirst bit rate described above. This detail also applies to a receivingoperation to receive data (E) (step S60) to be described later. Thesecond demodulation process is a demodulation process having a higherbit error rate than the first demodulation process.

Having finished the receiving operation to receive data (D), the sensorcontroller 31 determines whether it has received a burst signal, data(A), or data (D) or not (step S42). If the sensor controller 31determines that it has not received any of them as a result, it sets thestate flag to “0” (step S43), after which control returns to step S10.Step S43 indicates a process in which the sensor controller 31 fails todetect downlink signals for the reason that the stylus 2 has left thesensing range SR depicted in FIG. 1, for example. If the sensorcontroller 31 determines that it has received any one of them in stepS42, then the sensor controller 31 determines whether it has receivedall (48 bits) of the fragments (12-bit data) of a unique ID that can bereceived via data (D) or not (step S44). If the sensor controller 31determines that there are some fragments (remaining data) not yetreceived, then it determines a command that instructs the stylus 2 tosend a unique ID (requesting ID) as a command to be sent to the stylus 2(step S45), after which control goes back to step S10. If the sensorcontroller 31 determines that it has received all of the fragments (noremaining data) in step S44, then it sets the state flag to “4” (stepS46). The sensor controller 31 determines a command that instructs thestylus 2 to send data other than a unique ID (requesting DT) as acommand to be sent to the stylus 2 (step S47), and then control returnsto step S10.

If the state flag referred to in step S10 is “4,” then the sensorcontroller 31 sends a command signal representing a command determinedin steps S39, S47 or steps S57, S64 to be described later (step S50).Thereafter, the sensor controller 31 successively performs receivingoperations to receive a burst signal and data (A) (steps 551 a and S51b). When the sensor controller 31 receives a burst signal, it derivespositional coordinates of the stylus 2 on the basis of the detectedintensities of the received burst signal at the linear electrodes 30Xand 30Y.

Having finished the receiving operations to receive a burst signal anddata (A), the sensor controller 31 determines whether the stylus 2 is inhover state or not by confirming the state information State included indata (A) (step S52). If the sensor controller 31 determines that thestylus 2 is in hover state, then the sensor controller 31 performs areceiving operation to receive data (C) (step S53).

When the receiving operation to receive data (C) is over, the sensorcontroller 31 performs a process of detecting a finger touch over a timeperiod Tf (step S54) and determines whether it has received it hasreceived a burst signal, data (A), or data (C) or not (step S55). If thesensor controller 31 determines that it has not received any of them asa result, it sets the state flag to “0” (step S56), after which controlreturns to step S10. Step S56 indicates a process in which the sensorcontroller 31 fails to detect downlink signals for the reason that thestylus 2 has left the sensing range SR depicted in FIG. 1, for example.If the sensor controller 31 determines that it has received any one ofthem in step S55, then the sensor controller 31 determines a commandthat instructs the stylus 2 to send data other than a unique ID(requesting DT) as a command to be sent to the stylus 2 (step S57), andthen control returns to step S10.

If the sensor controller 31 determines that the stylus 2 is not in hoverstate (is in contact state) in step S52, then the sensor controller 31performs a receiving operation to receive data (E) (step S60). Asdepicted in FIG. 13, the receiving operation is carried out in a mannerto encroach slightly on the time period kept for detecting a fingertouch. The sensor controller 31 carries out a process of detecting afinger touch using a time period remaining after step S60 (step S61).

Having finished the receiving operation to receive data (E), the sensorcontroller 31 determines whether it has received a burst signal, data(A), or data (E) or not (step S62). If the sensor controller 31determines that it has not received any of them as a result, it sets thestate flag to “0” (step S63), after which control returns to step S10.Step S63 indicates a process in which the sensor controller 31 fails todetect downlink signals for the reason that the stylus 2 has left thesensing range SR depicted in FIG. 1, for example. If the sensorcontroller 31 determines that it has received any one of them in stepS62, then the sensor controller 31 determines a command that instructsthe stylus 2 to send data other than a unique ID (requesting DT) as acommand to be sent to the stylus 2 (step S64), and control returns tostep S10.

Although not depicted, the sensor controller 31 determines whether ithas received all of the fragments (1-bit data) of a serial number SNthat can be received via data (E) or not, in parallel to the executionof step S64. If the sensor controller 31 determines that it has receivedall of the fragments, then it combines the received fragments of aserial number SN as well as the received fragments of a unique IDreceived in step S40 that has been repeatedly carried out, to therebyrecover the unique ID and store the recovered unique ID. In this case,the sensor controller 31 determines the order in which to combine thefragments on the basis of frame index numbers FN sent with the fragmentsof a serial number SN, and determines the order in which to combine thefragments on the basis of frame index numbers FN sent with the fragmentsof a unique ID. The position of a serial number SN in a unique ID isspecified in advance.

The above process of recovering information is also applicable to penpressure data P. Specifically, as described above, the stylus 2 sendspen pressure data P as divided over a plurality of frames. The sensorcontroller 31 is able to determine the order in which to combine thefragments of the pen pressure data P on the basis of frame index numbersFN received with the fragments of the pen pressure data P.

The processes of the sensor controller 31 that correspond to the processof the stylus 2 which is depicted in FIG. 11 have been described above.Next, a specific process in which the controller 90 of the stylus 2makes the bit rate of data (B), (C), and (A) sent in hover state (thesecond bit rate) smaller than the bit rate of data (D) and (E) sent incontact state (the first bit rate) will be described in detail belowwith reference to FIGS. 14 through 19.

FIG. 14 is a diagram depicting a first example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2. The transmitter 75 of the stylus 2 in this example is arrangedto modulate a carrier signal with data to be sent according to the samemodulation process regardless of the state which the stylus 2 is in.Specifically, the transmitter 75 modulates a carrier signal having afixed frequency with data to be sent according to amplitude modulation(including on-off modulation) or phase modulation. The controller 90controls the transmitter 75 such that the modulation rate (the number oftimes which the carrier signal is modulated per unit time) for data (D)and (E) is larger than the modulation rate for data (A) through (C) (4:1in the example depicted in FIG. 14). As a result, inasmuch as the bitrate of data (D) and (E) (the first bit rate) is larger than the bitrate of data (A) through (C) (the second bit rate), it is possible tosend a large volume of data such as pen pressure data P, etc., which isdifferent from switch information SW1 depicted in FIG. 10, for example,in contact state. At the same time, it is possible to reducedemodulation errors and bit value decision error rates in the sensorcontroller 31 with respect to first digital values (the switchinformation SW1 depicted in FIG. 10, etc.) sent in hover state, comparedwith those sent in contact state. The modulation rate may be changed bymaking the transmission time period in which the data isamplitude-modulated or phase-modulated with the switch information SW1,for example, longer in hover state than in contact state.

FIG. 15 is a diagram depicting a second example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2. In this example, the controller 90 controls the transmitter 75to send each bit of data (D) and (E) just once and send each bit of data(A) through (C) repeatedly four times. This control scheme may have anencoding process that gives more redundancy (for error correction) inhover state or that reduces the modulation rate in hover state asdepicted in FIG. 14. From the standpoint of an amount of data that isessentially sent, the bit rate of data (D) and (E) sent (the first bitrate) is larger than the bit rate of data (A) through (C) (the secondbit rate described above), so that it is possible also in this exampleto send data including a large number of items of information such aspen pressure data P, etc., which is different from switch informationSW1 in contact state, and at the same time to reduce decision errorrates in the sensor controller 31 with respect to first digital values(the switch information SW1 depicted in FIG. 10, etc.) sent in hoverstate, compared with those sent in contact state.

The encoding process that gives more redundancy for error correction hasa redundancy ratio that may not necessarily be N:1 (N is an integer of 2or larger) insofar as it is larger in hover state than in contact state.For example, the same information may be repeated M times (M is aninteger of 2 or larger) in contact state and may be repeated N times(N>M) in hover state.

FIG. 16 is a diagram depicting a third example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2. In this example, the controller 90 controls the transmitter 75to add a check sum CS (first error detecting code) to the end of a datasignal. For sending data (A) through (C), the number of bits of theadded check sum CS is made larger than the number of bits of the addedcheck sum CS that sends data (D) and (E). Specifically, to data having asize (which is assumed to be of n bits) commensurate with a transmissiontime period td, there is added a check sum CS having a size commensuratewith a transmission time period tc1 for data (A) through (C), or a checksum CS having a size commensurate with a transmission time period tc2(<tc1) for data (D) and (E). Since a bit rate indicates the number ofbits sent per unit time, the bit rate of data (A) through (C) (the firstbit rate) is represented by n/(td+tc2) and the bit rate of data (D) and(E) (the second bit rate) is represented by n/(td+tc1). Since tc1>tc2,the latter bit rate (=n/(td+tc1)) is of a value smaller than the formerbit rate (=n/(td+tc2)). According to the present example, therefore, thesecond bit rate is of a value smaller than the first bit rate.

FIG. 17 is a diagram depicting a fourth example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2. In this example, the stylus 2 uses either phase modulation(specifically, binary phase shift keying (BPSK)) or amplitude modulationas a modulation process (second modulation process) for data (A) through(C), and uses amplitude phase modulation (specifically, 4 quadratureamplitude modulation (QAM)) as a modulation process (first modulationprocess) for data (D) and (E). In other words, different modulationprocesses are used for data (A) through (C) and data (D) and (E) formaking the bit rate of data (A) through (C) smaller than the bit rate ofdata (D) and (E). The first modulation process has a smaller bit errorrate than the second modulation process. Specifically, in the exampledepicted in FIG. 17, the ratio of the bit rate of data (D) and (E) (thefirst bit rate) and the bit rate of data (A) through (C) (the second bitrate) is 2:1. According to the present example, therefore, the secondbit rate is also of a value smaller than the first bit rate.

FIG. 18 is a diagram depicting a fifth example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2. The stylus 2 in this example, as with the stylus 2 in thefourth example, uses either phase modulation (specifically, BPSK) oramplitude modulation as a modulation process for data (A) through (C),and uses amplitude phase modulation as a modulation process for data (D)and (E). The amplitude phase modulation according to the present exampleexpresses a first bit with phase (0 degree or 180 degrees) and expressesa second bit with amplitude (multiplied by 1 or multiplied by 2). In thepresent example, as with the fourth example, since the ratio of the bitrate of data (D) and (E) (the first bit rate) and the bit rate of data(A) through (C) (the second bit rate) is 2:1, the second bit rate is ofa value smaller than the first bit rate.

FIG. 19 is a diagram depicting a sixth example of processes of sendingdata (A) through (C) and data (D) and (E), which are carried out by thestylus 2. This example relates to the transmission of a command signalfrom the sensor controller 31 and the transmission of downlink signalsfrom the stylus during a blank period in which the display panel havingthe linear electrodes 30X and 30Y disposed therein is de-energized. FIG.19(a) depicts a frame Frame_1 corresponding to a first blank period andFIG. 19(b) depicts a frame Frame_2 corresponding to a second blankperiod that follows the first blank period. In each of FIGS. 19(a) and19(b), an encircled numeral “1” corresponds to data (B) and (C), whereasan encircled numeral “2” corresponds to data (D) and (E).

For sending data (D) and (E), the stylus 2 according to this examplesends 14 bits of information using two frames Frame_1, Frame_2. Morespecifically, in the frame Frame_1, the stylus 2 sends 1-bit data data1through data6 following 2-bit information serving as state informationindicating that the stylus 2 is in hover state or in contact state, andin the frame Frame_2, the stylus 2 sends 1-bit data data7 throughdata14. The 2-bit information serving as the state information placedinitially in the frame Frame_1 is specifically “01” or “10,” and isplaced for the sensor controller 31 to distinguish between data (D) and(E) and data (B) and (C).

For sending data (B) and (C), the stylus 2 sends 2 bits of informationusing two frames Frame_1, Frame_2. More specifically, in the frameFrame_1, the stylus 2 sends a first bit of information (“0” or “1”)eight times, and in the frame Frame_2, the stylus 2 sends a second bitof information (“0” or “1”) eight times.

In this example, in other words, the stylus 2 sends each bit of data tobe sent just once for data (D) and (E), and sends each bit of data to besent repeatedly eight times for data (B) and (C). The stylus 2 operatingin this manner is the same as the stylus 2 according to the secondexample depicted in FIG. 15 except that the number of repetitions isdifferent. According to the present example, therefore, the second bitrate is of a value smaller than the first bit rate.

As described above, the stylus 2 according to the present embodimentmakes it possible to make the bit rate of data (B) and (C) sent in hoverstate (the second bit rate) smaller than the bit rate of data (D) and(E) sent in contact state (the first bit rate). Consequently, the noiseresistance in hover state in which the SN ratio of downlink signalstends to be poor is improved, resulting in advantages including areduction in the non-detection ratio of downlink signals, a reduction inthe bit error detection ratio at the time downlink signals are modulatedor decoded, and a reduction in the decoding error ratio while takingerror correction into consideration. Thus, even if downlink signals aresent with the same transmission intensity as in contact state, thepossibility of a failure to receive downlink signals in hover state canbe lowered.

Furthermore, since data (A) is sent at the same small bit rate as data(B) regardless of the state which the stylus 2 is in, the sensorcontroller 31 can reliably receive state information State regardless ofthe state which the stylus 2 is in. Therefore, the receiving operation(the first or second demodulation process described above) of the sensorcontroller 31 can be changed reliably in accordance with the bit rate ofdownlink signals, so that the stylus 2 can reliably send data (B)through (E) to the sensor controller 31.

Moreover, as depicted in FIG. 10, since each frame has a frame indexnumber FN, when the stylus 2 sends large-size data such as a unique IDor pen pressure data P as divided over a plurality of frames, the sensorcontroller 31 that receives those data can appropriately recover theinformation on the basis of the frame index numbers FN even if thedivided information is not received in order.

Although the preferred embodiment of the present disclosure has beendescribed above, the present disclosure is not limited to theembodiment, but can be reduced to practice in various forms withoutdeparting from the scope thereof.

For example, according to the above embodiment, a burst signal and data(A) are sent immediately before each of data (B) through (E). However,the transmission of a burst signal and data (A) immediately before data(D) and (E) may be omitted, for example.

In the above embodiment, the stylus 2 sends state information State inall frames. However, when two or more frames are sent in succession,state information State may be included in the first one of the two ormore frames, and state information State may not be included in thesubsequent frames following the first frame. More specifically, stateinformation State may not be sent (or its transmission may be omitted)in other frames than the frame sent first in a superframe. In this case,the sensor controller 31 may store state information State received inthe first frame and apply the stored state information State to thesubsequent frames. The transmission of state information State shouldpreferably be omitted only when the stylus 2 is in contact state.

Though not particularly described in the above embodiment, the state ofthe stylus 2 that is determined as the contact state in step S85depicted in FIG. 11 may be called “unique ID transmission mode,” andstate of the stylus 2 that is determined as the contact state in stepS90 depicted in FIG. 11 may be called “serial number transmission mode.”In this case, the controller 90 of the stylus 2 controls the transmitter75 to send the part of the unique ID of the stylus 2 that excludes theserial number by way of data (D) in a superframe compatible with theunique ID transmission mode, and controls the transmitter 75 to send theserial number SN by way of data (E) in a superframe compatible with theserial number transmission mode.

In the above embodiment, the stylus 2 determines the content of acommand signal sent from the sensor controller 31, determines whetherthe command is a command (ID) that instructs the stylus 2 to send aunique ID or a command (DT) that instructs the stylus 2 to send dataother than a unique ID, and selectively sends a unique ID or data otherthan a unique ID depending on the result of the determination. Thestylus 2 may make such determination on the basis of its own state(e.g., the operated state of a switch SW1). For example, if the switchSW1 is not operated (i.e., the user is not touching an operating section(switch SW1, switch SW2, etc.) of the stylus 2 at all), the stylus 2 maysend a unique ID, and if the switch SW1 is operated (i.e., it is turnedon), the stylus 2 may send data other than a unique ID (information ofthe switch SW1 or the like). When the stylus 2 is not operated,therefore, it can complete the transmission of a unique ID that has arelatively large amount of information. A unique ID that is sent inhover state may include the information of a serial number SN that issent in contact state.

When the sensor controller 31 is to send an uplink signal includingoptional data such as a command or the like (third digital value), itmay add a check sum corresponding to the data (second error detectingcode). In this case, the stylus 2 should preferably determine whether ithas correctly received the data sent by the sensor controller 31 or not,using the check sum. The stylus 2 may send a long burst signal, a burstsignal, and data (A) through (E) regardless of the result of thedetermination (even if the result of the determination is negative).

First and second modifications of the above embodiment will be describedbelow.

FIG. 20 is a diagram depicting an arrangement of a stylus 2 according toa first modification of the above embodiment. A sensor controller 31 andthe stylus 2 according to the present modification are different fromthose of the above embodiment in that they, for the purpose oftransmission of uplink signals, use wireless communications not on thecapacitive coupling principle. The stylus 2 is different from that ofthe above embodiment in that it supports the transmission of two kindsof downlink signals DS1 and DS2 whose carrier signals are of differenttypes from each other. Both the downlink signals DS1 and DS2 are capableof sending a long burst signal, a burst signal, and data (A) through (E)as described above. The stylus 2 selectively uses the downlink signalsDS1 and DS2 depending on the kind of the sensor controller 31 which isin close proximity thereto. The arrangement of the stylus 2 according tothe present modification will be described in detail below withreference to FIG. 20.

As depicted in FIG. 20, the stylus 2 according to the presentmodification has an electrode 21, a signal processor 24, a power supply25, an amplifier 26, and a receiver 27.

The receiver 27 is a functional section capable of performingcommunication by way of Bluetooth® (registered trademark) as wirelesscommunication. According to the present modification, the receiver 27receives an uplink signal that the sensor controller 31 has sent by wayof Bluetooth® (registered trademark).

The signal processor 24 is a functional section having a function toselectively send the two kinds of downlink signals DS1 and DS2 and afunction to receive an uplink signal US via the receiver 27.Specifically, the signal processor 24 has a controller 91, a voltagebooster 92, an oscillator 93, and a switch 94.

The voltage booster 92 has a function to boost a DC voltage suppliedfrom the power supply 25, generating a DC voltage V1. According to aspecific example, the voltage booster 92 includes a DC-DC converter or acharge pump circuit.

The oscillator 93 has a function to perform an oscillating operationbased on the DC voltage supplied from the power supply 25 to generate anunmodulated sine-wave signal (carrier signal) that oscillates at apredetermined frequency. The amplifier 26 has a function to amplify thesine-wave signal generated by the oscillator 93 with a predeterminedamplification factor, generating an unmodulated sine-wave signal v2. Asdepicted in FIG. 20, the amplifier 26 should preferably include amamplifying circuit made up of a transformer and capacitors.

The switch 94, which includes a one-circuit three-contact switchelement, has a terminal “a” connected to the output terminal of thevoltage booster 92, a terminal “b” connected to the output terminal ofthe amplifier 26, a terminal “g” connected to a power supply line thatis supplied with a ground potential, and a common terminal c connectedto the electrode 21.

The controller 91 includes an IC, which supplies a control signal Ctrlthat controls the switch 94 and which controls the receiver 27 toreceive an uplink signal sent by the sensor controller 31. Thecontroller 91 operates with electric power supplied from the powersupply 25. According to a specific example, the controller 91 mayinclude an application specific integrated circuit (ASIC) or an MCU. Thecontroller 91 determines the kind of a downlink signal (the downlinksignal DS1 or the downlink signal DS2) used to send a long burst signal,a burst signal, and data (A) through (E) as depicted in FIG. 10, on thebasis of the content of an uplink signal received via the receiver 27 orthe fact that no uplink signal is received (in a case where the sensorcontroller 31 is designed to operate with only unidirectionalcommunication from the stylus 2 to the sensor controller 31). As withthe controller 90 depicted in FIG. 8, the controller 91 also determinesa transmission and reception schedule for various signals, etc., andcontrols the switch 94 based on the determined transmission andreception schedule.

For sending the downlink signal DS1, the controller 91 controls theswitch 94 to function as a first switch provided between the outputterminal of the voltage booster 92 and the electrode 21. Specifically,the controller 91 controls the switch 94 to switch between a state inwhich the terminal “a” is connected to the common terminal “c” and astate in which the terminal “g” is connected to the common terminal “c.”The state in which the terminal “a” is connected to the common terminal“c” corresponds to a state in which the first switch is on, and thestate in which the terminal “g” is connected to the common terminal “c”corresponds to a state in which the first switch is off.

For sending a burst signal or a long burst signal using the downlinksignal DS1, the controller 91 controls the switch 94 to performswitching operations periodically in predetermined periodic cycles. Whenthe terminal “a” is connected to the common terminal “c,” the DC voltageV1 comes through as the output voltage of the switch 94. When theterminal “g” is connected to the common terminal “c,” the groundpotential comes through as the output voltage of the switch 94.Consequently, the switch 94 outputs an unmodulated pulse train signalthat serves as a long burst signal or a burst signal.

For sending a data signal using the downlink signal DS1, the controller91 controls the switch 94 to perform a switching operation depending ondata, such as a unique ID, pen pressure data P, or switch information SWwhich indicates whether a switch (not depicted) on the stylus 2 is on oroff, to thereby generate a data signal which includes a pulse trainsignal modulated with the data. Specific methods of modulating a pulsetrain signal by the controller 91 may include on-off modulation andfrequency modulation.

For sending the downlink signal DS2, the controller 91 controls theswitch 94 to function as a second switch provided between the outputterminal of the amplifier 26 and the electrode 21. Specifically, thecontroller 91 controls the switch 94 to switch between a state in whichthe terminal “b” is connected to the common terminal “c” and a state inwhich the terminal “g” is connected to the common terminal “c.” Thestate in which the terminal “b” is connected to the common terminal “c”corresponds to a state in which the second switch is on, and the statein which the terminal “g” is connected to the common terminal “c”corresponds to a state in which the second switch is off.

For sending a burst signal or a long burst signal using the downlinksignal DS2, the controller 91 controls the switch 94 to fixedly connectthe common terminal “c” to the terminal “b.” Therefore, the switch 94outputs the unmodulated sine-wave signal v2 that serves as a long burstsignal or a burst signal.

For sending a data signal using the downlink signal DS2, the controller91 controls the switch 94 to perform a switching operation depending ondata such as a unique ID, pen pressure data P, or switch information SW,to thereby generate a data signal which includes a sine-wave signalmodulated with the data. A specific method of modulating a sine-wavesignal by the controller 91 may include on-off modulation.

According to the present modification, as described above, Bluetooth®(registered trademark) can be used to send and receive an uplink signal.Although the example using Bluetooth® (registered trademark) has beendescribed above, proximity wireless communications other than Bluetooth®(registered trademark) may be used to send and receive an uplink signal.

According to the present modification, the stylus 2 is capable ofperforming bidirectional or unidirectional communication between itselfand a plurality of different types of sensor controllers 31 byselectively using the downlink signals DS1 and DS2.

FIG. 21 is a flowchart of an operation sequence of a stylus 2 accordingto a second modification of the above embodiment. The stylus 2 accordingto the present modification is different from the stylus according tothe above embodiment in that it determines its own state on the basis ofthe received intensity of an uplink signal rather than the pen pressurebeing detected by the pen pressure detection sensor 23. Operation of thestylus 2 according to the present embodiment primarily with respect tothe differences from the above embodiment will be described in detailbelow with reference to FIG. 21.

The stylus 2 according to the present modification determines anintensity in steps S100 and S101 instead of determining a state in stepsS85 and S92 depicted in FIG. 11. Steps S100 and S101 are steps ofdetermining the received intensity of the command signal detected inprevious step S80.

If the stylus 2 determines that the received intensity is smaller than apredetermined value (i.e., “weak”) in step S100, then the stylus 2determines its own state as the hover state. As with the case ofdeciding the hover state in step S85, the stylus 2 sends a burst signaland data (A) and (B) (steps S86 through S88). If the stylus 2 determinesthat the received intensity is equal to or larger the predeterminedvalue (i.e., “strong”) in step S100, then the stylus 2 determines itsown state as the contact state. As with the case of deciding the contactstate in step S85, the stylus 2 sends a burst signal and data (A) and(D) (steps S89 through S91).

If the stylus 2 determines that the received intensity is smaller thanthe predetermined value (i.e., “weak”) in step S101, then the stylus 2determines its own state as the hover state. As with the case ofdeciding the hover state in step S92, the stylus 2 sends a burst signaland data (A) and (C) (steps S93 through S95). If the stylus 2 determinesthat the received intensity is equal to or larger the predeterminedvalue (i.e., “strong”) in step S101, then the stylus 2 determines itsown state as the contact state. As with the case of deciding the contactstate in step S92, the stylus 2 sends a burst signal and data (A) and(E) (steps S97 through S99).

As described above, the stylus 2 according to the present modificationis capable of determining its own state on the basis of the receivedintensity of a command signal rather than a pen pressure. Therefore, thepresent disclosure is applicable to a stylus 2 that has no pen pressuredetecting function, for example.

In the present modification, the example in which the stylus 2determines its own state based on the received intensity of an uplinksignal (specifically, a command signal) has been described. However, thesensor controller 31 may determine the state of the stylus 2 based onthe received intensity of a downlink signal in the sensor controller 31,and indicate the result to the stylus 2. In this case, preferably, thesensor controller 31 includes state information indicating the state ofthe stylus 2 as part of a command signal, and the stylus 2 receives anddecodes the state information, thereby acquiring its own state.

DESCRIPTION OF REFERENCE SYMBOLS

-   2: Stylus-   3: Electronic device-   20: Core body-   21: Electrode-   22, 44 x, 44 y, 62: Switch-   23: Pen pressure detection sensor-   24: Signal processor-   25: Power supply-   26: Amplifier-   27, 50, 71: Receiver-   30: Sensor-   30X, 30Y: Linear electrode-   31: Sensor controller-   40: Selector-   41 x, 41 y: Conductor selecting circuit-   51: Amplifying circuit-   52: Detecting circuit-   53: Converter-   60, 75: Transmitter-   61: Pattern supply-   63: Spreading processor-   64: Code train holder-   65: Transmission guard-   70: Logic unit-   71 a: Waveform regenerator-   71 b: Correlation operator-   73: Modulator-   74: Voltage boosting circuit-   76: Switch-   90, 91: Controller-   92: Voltage booster-   93: Oscillator-   94: Switch-   FN: Frame index number-   Mode: Mode information-   Op: Inverted bit-   P: Pen pressure data-   RS: Reserved information-   SN: Serial number-   Start: Start flag-   State: State information-   SW1, SW2, SW3: Switch information

1. A stylus comprising: a core body; an electrode disposed adjacent tothe core body; a transmitter that sends a signal including a firstdigital value using the electrode; and a controller that determineswhether the stylus is in contact state in which the core body is held incontact with an operating surface or in hover state in which the corebody is not held in contact with the operating surface, controls thetransmitter to send the first digital value at a first bit rate when thestylus is determined to be in contact state, and controls thetransmitter to send the first digital value at a second bit rate smallerthan the first bit rate when the stylus is determined to be in hoverstate.
 2. The stylus according to claim 1, wherein the controllercontrols the transmitter to send the first digital value at the firstbit rate when the stylus is determined to be in contact state and at thesecond bit rate when the stylus is determined to be in hover state, bymaking a transmission time period used to send the first digital valueper bit shorter when the stylus is in contact state than when the stylusis in hover state.
 3. The stylus according to claim 2, wherein thecontroller controls the transmitter to send the first digital value atthe second bit rate when the stylus is determined to be in hover state,by making a modulation rate for the first digital value lower when thestylus is in hover state than when the stylus is in contact state. 4.The stylus according to claim 1, wherein the controller controls thetransmitter to send the first digital value at the first bit rate whenthe stylus is determined to be in contact state and at the second bitrate when the stylus is determined to be in hover state, by repeatedlysending one bit of the first digital value when the stylus is in hoverstate.
 5. The stylus according to claim 1, wherein the controllercontrols the transmitter to send the first digital value at the firstbit rate when the stylus is determined to be in contact state and at thesecond bit rate when the stylus is determined to be in hover state, bymaking a number of bits of a first error detecting code sent with thefirst digital value greater when the stylus is in hover state than whenthe stylus is in contact state.
 6. The stylus according to claim 1,wherein the controller controls the transmitter to send the firstdigital value at the first bit rate when the stylus is determined to bein contact state and at the second bit rate when the stylus isdetermined to be in hover state, by controlling the transmitter tomodulate the first digital value according to a first modulation processwhen the stylus is in contact state and according to a second modulationprocess whose bit error rate is smaller than the first modulationprocess when the stylus is in hover state.
 7. The stylus according toclaim 1, wherein the controller controls the transmitter to send thefirst digital value at the first bit rate when the stylus is determinedto be in contact state and at the second bit rate when the stylus isdetermined to be in hover state, by controlling the transmitter tomodulate the first digital value using amplitude phase modulation whenthe stylus is in contact state and using either amplitude modulation orphase modulation when the stylus is in hover state.
 8. The stylusaccording to claim 1, wherein the controller controls the transmitter tosend the signal including the first digital value during a blank periodin which a display panel is de-energized, and the controller controlsthe transmitter to send the first digital value at the first bit ratewhen the stylus is determined to be in contact state and at the secondbit rate when the stylus is determined to be in hover state, by makingan amount of information sent during one blank period smaller when thestylus is in hover state than when the stylus is in contact state. 9.The stylus according to claim 1, wherein the controller controls thetransmitter to send state information indicative of whether the stylusis determined to be in contact state or in hover state.
 10. The stylusaccording to claim 9, wherein the controller controls the transmitter tosend the signal in units of frames, and the state information is placedbefore the first digital value in one frame.
 11. The stylus according toclaim 10, wherein the controller controls the transmitter to send thestate information at the second bit rate regardless of whether thestylus is determined to be in contact state or in hover state, and thecontroller controls the transmitter to send the state information at thesecond bit rate and thereafter send the first digital value at the firstbit rate when the stylus is determined to be in contact state.
 12. Thestylus according to claim 9, wherein the controller controls thetransmitter to send the first digital value at the first bit rate whenthe stylus is determined to be in contact state, by repeatedly sendingone bit of the first digital value when the stylus is determined to bein hover state, and the controller sends the state information byinitially sending a plurality of digital values which are different fromeach other when the stylus is determined to be in contact state.
 13. Thestylus according to claim 10, further comprising a pen pressure detectorthat detects a pen pressure applied to the core body, wherein thecontroller controls the transmitter to send a second digital valuerepresenting the pen pressure detected by the pen pressure detector,subsequently to the state information in one frame, at the first bitrate when the stylus is determined to be in contact state.
 14. Thestylus according to claim 9, wherein the controller controls thetransmitter to send the signal in a unit of a superframe including apredetermined number of frames, and the controller controls thetransmitter to send the state information in an initially sent one ofthe frames in the superframe and not to send the state information inframes other than the initially sent one of the frames in thesuperframe.
 15. The stylus according to claim 14, wherein the superframecorresponds to an operating period of a display process for a displaypanel.
 16. The stylus according to claim 14, wherein the controller, tosend two or more of the frames in succession, controls the transmitterto include the state information in a first one of the two or more ofthe frames and not to send the state information in subsequent framesfollowing the first one of the two or more of the frames.
 17. The stylusaccording to claim 16, wherein the controller controls the transmitterto send a serial number, which forms part of a unique ID assigned to thestylus, when the stylus is determined to be in contact state.
 18. Thestylus according to claim 17, wherein the controller controls thetransmitter to send the serial number as divided over a predeterminednumber of frames in the superframe.
 19. The stylus according to claim17, wherein the serial number indicates information for a sensorcontroller to identify a plurality of styluses which are in use with thesensor controller.
 20. The stylus according to claim 17, wherein theserial number indicates a pen tip setting type of the stylus.
 21. Thestylus according to claim 16, wherein the controller operates in one ofa unique ID transmission mode and a serial number transmission mode persuperframe when the stylus is determined to be in contact state, and thecontroller controls the transmitter to send part of the unique ID thatexcludes the serial number in a superframe in the unique ID transmissionmode, and controls the transmitter to send the serial number in asuperframe in the serial number transmission mode.
 22. The stylusaccording to claim 16, wherein the controller controls the transmitterto send, in each of the predetermined number of frames, a frame indexnumber representing order of the frames in the superframe.
 23. Thestylus according to claim 1, further comprising a receiver that receivesfrom a sensor controller an uplink signal including a third digitalvalue and a second error detecting code corresponding to the thirddigital value, wherein the receiver determines whether the third digitalvalue has been correctly received or not, using the second errordetecting code after having received the uplink signal, and thecontroller controls the transmitter to send a downlink signal regardlessof a result of the determination by the receiver.
 24. The stylusaccording to claim 1, wherein the controller controls the transmitter tosend an inverted bit immediately after a predetermined number of bits,the inverted bit being generated by inverting the last one of thepredetermined number of bits.
 25. A stylus comprising: a core body; anelectrode disposed adjacent to the core body; a transmitter that sends asignal including a first digital value using the electrode; and acontroller that controls the transmitter, wherein the controllercontrols the transmitter to send the signal in a unit of a superframeincluding a predetermined number of frames, and the controller controlsthe transmitter to send, in each of the predetermined number of frames,a frame index number representing order of the frames in the superframe.26. The stylus according to claim 25, wherein the controller controlsthe transmitter to send a serial number, which forms part of a unique IDassigned to the stylus, as divided over the predetermined number offrames in the superframe.
 27. A stylus comprising: a core body; anelectrode disposed adjacent to the core body; a transmitter that sends asignal including a first digital value using the electrode; and acontroller that determines whether the stylus is in contact state inwhich the core body is held in contact with an operating surface or inhover state in which the core body is not held in contact with theoperating surface, controls the transmitter to send the first digitalvalue according to a first signal transmission process when the stylusis determined to be in contact state, and controls the transmitter tosend the first digital value according to a second signal transmissionprocess whose decoding error rate is smaller than the first signaltransmission process when the stylus is determined to be in hover state.28. A sensor controller comprising: memory including computer-executableinstructions, and one or more processors configured to execute theinstructions to perform: acquiring state information of a stylus from asignal received from the stylus according to a first demodulationprocess; acquiring a first digital value included subsequently to thestate information according to the first demodulation process if thestate information indicates that the stylus is in hover state; andacquiring the first digital value included subsequently to the stateinformation according to a second demodulation process whose bit errorrate is higher than the first demodulation process if the stateinformation indicates that the stylus is in contact state.